[Freeswitch-users] session, channels, calls

Hello all, i've been reading the wiki, book, and using some google foo in trying to understand what freeswitch considers sessions, calls, and channels. So far i've gathered a session is just a connection between FreeSWITCH and a protocol, but i haven't been able to figure out what a channel is considered and what a call is considered. I know this is probably super simple, but i havent been able to make the connection yet as to what they are. Thanks in advance. Anish