One interesting aspect of TFC is the interdependence it breeds amongst teammates. After picking a team (i.e. red team or blue team), players pick a *class*. After dying (which is normal), players can pick a new class. Each class, listed below, has its own advantages and shortcomings.
Several on-line gaming leagues exist, where players compete each week for dominance through their teams, or clans. Since TFC is naturally a Team game, it lends itself well to this aspect.
But you don't have to be in a formal team to play TFC right now. All you need is a copy of Half-Life. Pick up a server browser like The All-Seeing Eye and join any public server. It is likely populated with players like you--if not, pick another--and start shooting away. For beginners, a class like soldier or HWGuy is recommended.
Since its release in 1999, the developers of the game, Valve Software, have introduced various changes into the game. Perhaps the most momentous was TFC 1.5, which, amongst other things, "rebalanced" the game in an effort to make certain classes less dominant or more competitive.
Serious groups of players, clans, have seen the rise of playing for money in tournaments like The CPL. However, TFC's popularity has probably seen its peak, and CPL prizes have not seen the heights of $100,000 for the Counter-Strike champion.