It's free!
Basically in F.E.A.R. Combat you fight other players in death match, TDM, capture the flag, and more, like slow-mo games using the enhanced reflexes from single player. You can start off with the majority of the weapons (only choosing one of course) but there are also 3 super weapons hidden in each map making for fun tactics, but may also lead to camping. The main downside is well...it's free. With that, you get the crowd of people who shouldn't be playing but do so regardless because they lied about their age on initial sign up or their mommy's and daddy's let them, luckily theres no mic support (last I checked)
Either way its a great game every FPS should already have, but those on a budget its fun, multilayer, and a good competitor to Enemy Territory.