About Channel in Asterisk?

I use a softphone (X-lite) to make call to Asterisk, and I see the Channel is on the picture here.

But I don’t know about the Channel column. it always change ? I see SIP/101-09bb7f90, SIP/101-09bbc118, SIP/101-09b93fb8, and SIP/101-09bb7f90 after trying to call many times. How to get the name of this channel, how to change this channel to a specific name? When I want to originate a call, I need to know about the Channel name, but It always change, how to make call?
I have 2 SIP account: 101 and 102. I want to call from 101 to 102 and I need to know Context, Channel, CallerID and Extend.