Assuming that you're referring to authoring the production master, yes - It's essentially the sequencing and assembly of a compliant and "clean" production master.
Who does it... well... anybody from the mastering engineer to the duplication/replication house. It depends.
Authoring is making a master CD that will be used as the source for duplication or replication. This could involve any or all of the following:
* confirming that the levels are roughly even (though this should be fixed by a mastering engineer).
* setting the track order.
* adding ISRC codes to each track.
* adding CD-TEXT if desired.
* adjusting head and tail gaps for optimal performance
* doing any special tricks (e.g. inserting audio into the track 1 pregap)