DarkRP is a non-serious roleplay gamemode developed by FPtje (Falco Peijnenburg) over the course of the last 8 years, over this time it has grown into one of, if not the biggest gamemode in all of Garry's Mod.
DarkRP by default has an Administration Mod called FAdmin and a Prop Protection System called FPP (Falco's PP)
Modifying DarkRPs default settings is simplified by using an addon called DarkRPModification created by FPtje to stop people from editing the core files and breaking stuff
DarkRP is expansive even beyond the DarkRP gamemode itself, people modify it into other Roleplay gamemodes such as the following
Modifying the default DarkRP gamemode into other gamemodes is not recommended and you should use a different Roleplay Base designed to be modified or use the DarkRP Derived.
Because DarkRP is used so widely a lot of paid and non-paid addons support it unlike other Roleplay Gamemodes that are out there making it perfect for a quick plug and play server
f1 - Motd Panel or Information
f3 - Show Mouse
f4 - Main Panel
/ooc - Out Of Character (Global Chat)
/yell - Yell out, your text appearing in a larger area
/pm - Private message a player (/pm Player1 Hey you're pretty cool!)