I can't remember... can someone remind me plz

It depends upon the context. Typicaly a buffer is a holding area... probably in this case a software buffer where data is stored prior to moving to a different place or where data is kept in a temporary fashion to be reviewed or used later. In some cases a buffer is a place where information is coming in at a rate faster than the ultimate destination can accept it... therefore the buffer stored the information until the next step in the process asks for more.

The buffer in xolox is number of sources, or people it found with the file, that it hasnt yet attempted to connect to.