StarCraft II has two areas of gameplay, singleplay and multiplay.
Singleplay includes the Terran campaign called the Wings of Liberty, Challenges to test your skills in the arts of base defense, unit control, build order, and resource management, also you can play by yourself against computers and last but not least their is a tutorial for those who have never played before.
The campaign is composed of a series of missions where you play as the race known as the Terran, exiled prisoners from Earth who crashed in the Koprulu sector and created civilizations and had to build heavy duty war equipment to fight off two alien races.
Mar Sara Missions
The campaign begins on a planet called Mar Sara, where you play 3 missions.
Mission 1 destroy a dominion base to insight rebellion among the people.
Mission 2 take control of a mining crane, and steal an alien artifact from the dominion.
Mission 3 defend your base against zerg attacks for 20 minutes until your transportation can pick you up (aka the Hyperion).
After you are rescued by the Hyperion you take off and you see some different cinematics, you also find you have multiple missions that you can do, you can either start the Covert missions, or you can start the Colonist missions.
A bit different from the Mar Sara missions, the Colonist missions have Four total missions.
Mission 1 The Evacuation: Create troops and defend the colonists as they make their way to the transport ships. The enemy is the Zerg.
Mission 2 Outbreak: Defend your base by night, attack all infested buildings during the day.
Mission 3 Safe Haven: Defend the planet that you found for the colonists to live on. The protoss believe that a zerg disease has spread to the people of Haven and they wish to wipt them out, do not let them win.
Mission 4 Haven's Fall: This mission and mission 3 are choice missions (you get to choose either one or the other but not both, however you can come back later and do the other one) In this mission, rather than help the people of Haven you help the Protoss to purify the planet of anything with a zerg bioinfection.
The covert missions introduces a new character by the name of Tosh. He offers money in exchange for your services.
Mission 1 The Devil's Playground: This mission is not to tricky but it sure keeps you on your toes. Every few minutes or so their is a Lava surge which covers up the lower ground and kills anything on the ground. Also their are zerg running around that will attack you.
Mission 2 Welcome to the Jungle: In this mission you are up against a large group of Protoss that are like a cult. The mission objective is to collect several containers of terrazine gas, but the protoss don't appreciate your presense on their sacred ground, they won't make it any easier on you.
Mission 3/4 Once again you choose between two missions
Breakout: Help Tosh break into the biggest prison in the universe and free his buddies. To your disadvantage a Ghost operative named Nova tips the guards off that you will be their. In this mission you play as Tosh and learn how to use the abilitys of a Spectre.
Ghost of a Chance: In this mission you play as Nova a Ghost operative who has been tracking down Tosh for quite some time, you must help her to defeat Tosh's forces.
The rebellion missions are mostly planned and run by Matt Horner the captain of the Hyperion who just wants to live in a better world.
Mission 1 The Great Train Robbery: In this mission you are informed that the Dominion has dug up an artifact of some importance, your job is to hit and destroy every train that goes by until you find the artifact. This mission introduces Diamond Backs, who can attack while moving.
Mission 2 Cutthroat: In this mission you discover that the guy you hired to unlock the secrets of the artifact you found earlier is trying to sell the artifact back to the Dominion, you must work to gather enough minerals to hire a mercenary to help you beat him. This mission introduces Vultures.
Mission 3 Engine of Destruction: In this mission you invade a Domion Base and take over a new military weapon called the Odin, it has extreme fire power, you must defend the Odin while your buddy Tychus Finley opperates it and destroys the rest of the base.
Mission 4 Media Blitz: In this mission you must use the Odin to blow up domion forces and take control of the New Station, the reason for this is that the artifact you discovered earlier had a recording of Emporer Mengsk saying some things that would get him in big trouble, your goal is to broadcast this recording.
Mission 5 Piercing the shroud: This is the secret mission, it can only be unlocked by finding a secret message on the previous level. In this mission you must break into a secret lab and then escape knowing about the Hybrids.
The artifact missions are quite helpful throughout the campaign as they are a main source of cash, this series of missions puts you through the test against all three races to collect special alien artifacts.
Mission 1 Smash and Grab: In this mission you must smash through protoss lines in a race against the zerg to get to the artifact which is defended by three large statues with insane laser blasts.
Mission 2 The Dig: In this mission you must take control over an old moebius power drill, a huge laser drill with the power of the sun. You must defend your base until the laser drill can succesfully drill a hole through the powerfull temple doors guarding the artifact. This mission introduces Siege Tanks.
Mission 3 The Moebius factor: In this mission the Moebius foundation, the guys who have been paying you to collect artifacts for them, have been overrun with zerg. Most of them have escaped but what they really want is for you to destroy the Data cores so that Kerrigan, the Queen of Blades, does not find the coordinates to the next artifact. You must race against Kerrigan while struggling against zerg forces the whole time. This mission introduces medivac's, transportation flying units that can heal units.
Mission 4 Supernova: The next artifact is guarded by Protoss, but this time you must race the clock because this solar system's sun just went supernova and is about to destroy the whole planet.
Mission 5 Maw of the Void: In this mission the artifact is guarded by protoss on a space station, but the station is protected by rip fields, sheilds made of energy that will rip apart any mechanical unit that flys in. So in order to beat this you must use Battlecruisers which are so powerfull that it takes a while for the fields to tear them apart. You must fly in destroy the rip field generators, and then fight off a mothership to take the artifact.
These are the last missions
Mission 1Gates of Hell: In this mission you land on the zerg homeworld, but the army was split up all across the surface, your job is to gather a large army and then find and assist the general.
Mission 2Belly of the Beast: In this mission you must take a small group and head underground to place charges that will blow everything up and cause the underground chambers to flood with lava. This is so that later you won't have to worry about Nydus worms.
Mission 3Shatter the Sky: In this mission you must place charges on a sky platform to blow it up. This will prevent air attacks later on.
Mission 4All In: This is the Last mission. You must hold out until the fully completed artifact is charged up and ready to blow. This artifact is designed to destroy the zerg. You must hold off ground, air, and other attacks along with Kerrigan herself.