Fserve is just short for File Server. Anybody on an IRC channel could download a script to run an fserve. Using a trigger, other users on the channel could start a DCC Chat session with you. The chat session would be automated on your end, as it would be listing files and directories. The other user can request a file to be downloaded. A DCC Send would then begin, or they would be added to your Queue if all sends are already used up.