When you channel, you are creating a gateway for the spirit guides of the channel and the client to speak directly to the client. The guides take over the body of the channel and speak using the channel's voice to answer questions directly.
There are two kinds of channeling - semi-conscious and unconscious.
Semi-conscious channels are aware of what they are saying and can step in and take over the conversation if they need to. They will sometimes remember what is said after the session is over, but it tends to fade with time since they were not fully present to the messages.
Unconscious channels are unaware of what is being said in the session and have given over the complete use of their bodies to their guides. They will not remember what is said.