Starcraft is a Real-Time Strategy game originally only for PC and then Mac, for some reason Blizzard figured they could make a little money by also releasing it on the Nintendo 64, which sucked ass compared to the PC and Mac versions if anything just for the lack of online play and map editor. It sold a shitload of games, and is often cited as one of the best RTS' of all fucking time.
Terran: The good guys of the game, they are also the "Mario" in the gameplay aspect, as they are mostly all-around and can do pretty much any tactic in at least a decent manner. Ironically, not many people play as Terran as much as Toss or Zerg.
Protoss: The anti-heros slash secondary good guys of the game, most "Toss" players use a defense game, and build a bigass base so they may defend attacks and fully upgrade everything and get all researches. If this happens, the Toss player is now the most dangerous foe on the map, and must be killed quickly, or his forces who are as strong as Wario's ass will utterly obliterate your defenses if their attack is timed right.
Zerg: The bad guys of course, if you haven't figured it out already from their ugly faces. The Zerg are best at offense, and suck ass at defense which is apparent in their slower way of building bases. The key to most Zerg player's strategies is to build a crapload of Zerglings as fast as possible and overrun the opponent's base before they even know what raped their asshole. If a game runs long, a Zerg player will often find themselves on the ropes, especially if fighting Protoss. So get your goddamn shit together quickly, asshole.
Common "Use Map Settings" Maps
Alot of players mostly only played Starcraft for the "Use map settings" maps, which were a wide range of games that were not related to the usual RTS battle scenario.
Bunker Wars: Probably one of the oldest, if not THE oldest recurring game. It involves numerous players attacking eachother's lone(Or in some games two, or even three) bunker(s), while at the same time trying to destroy their opponent's bunker(s). Units were often automatically generated at the bunker, the units could be anything, but they're usually Marines(Which is how it was in the original game). In some incarnations or knockoffs, the players' current unit can be upgraded into a better unit if they kill enough of their opponent's units. Sometimes there is also a Missile Turret sanctioned near the bunker or directly on top of it, this is usually put here to make invisible units visible or to attack air units if they're upgradable to, though they are often left out, as sometimes players only have melee units who cannot attack air units.
OH MY FUCKING GOD THE ZERGLINGS: A defense game that involved players creating bases and making alot of units in a set amount of time to repel a huge Zergling attack that is spawned automatically at the end of the map and controlled by the CPU. There was also a "OH MY FUCKING GOD THE ULTRALISKS" version of the game, but of course with Ultralisks, the game is often found to be harder as the Ultralisk unit is MUCH stronger in comparison to the Zergling. There was also a Hydralisk version, but it never caught on, as some players thought it was even harder than the Ultralisk version.
Numerous Dragonball Z "reenactments": During the height of the TV show/anime Dragonball Z's popularity, alot of fans who played Starcraft made maps in order to renact or reinvent several story arcs, such as the Saiyan Saga, Frieza Saga, Cell Saga, etc. There were also maps based on movies, and Dragonball GT.
Coke Vs. Pepsi, Warcraft Vs. Starcraft, Marvel Vs. DC, etc.: This is also a very old concept, the objective was for a team of three players who represented a certain series/company/brand/etc. to destroy the other team of three players who were often the "rival" of said series/company/brand/etc. These concepts can be as casual as Pepsi vs. Coke, to outlandish ones such as cleaning products vs. germs. What seperated this game from any ordinary Starcraft game(Besides name changes) is that players may bring their units down to the bottom of their side of the map to get a better unit, such as bringing down ten marines to get an awesomer version of a marine.
Alot of _____ Defense games: Similar to OH MY FUCKING GOD THE ZERGLINGS, except the players would attempt to stop waves of computer controlled enemies from reaching the other side of the screen. The players were often on another plane away from the area where the CPU units were moving, but once in a while they may be on the same plane and try and block the CPU units, however this would often lead to the CPU units attacking the player to make an opening.
Stacked Cannon Defense: Just like the aforementioned Defense games, only this one expanded on a glitch that allowed Probes to stack buildings on one another in the middle of a game. The trick called for a "fog maker" which automatically put a fog of war over the player's units whether they were actually there or not, and also to put their Prope on a "force"(A team.). There the player would hit the force's designated hotkey and selected the currently fog of war'd Probe, and be able to constantly build Photon Cannons on top of eachother.
There were many other popular games out there, but this article shouldn't be that long.