The langauge used is a hangover from the old client/server model in which relatively dumb terminals accessed the main computer for all their requirements. The language for Peer to Peer networking is still developing.

Each computer on a p2p network is both a client (it accesses other computers for information) and a server (it provides information to other clients). Each computer is (or should be ) a host in that it hosts (holds) files for other computers to access.

So - on a p2p network 'client', 'server', 'host' and 'peer' all mean the same thing but are sometimes used to differentiate 'this' computer from 'that' computer.

There is a similar problem with uploading and downloading. What is uploaded from you is downloaded by me and vice versa.

Leaf Node and client are very nearly identical - except that a client doesn't have to be a leaf - but on the current network a client is much more likely to be a leaf to an ultrapeer than a true peer to another computer.

I hope that makes everything clear :-)

Mark