When a full band is tracking (or recording their part) in any studio, you will almost always track in the same order:
Almost every time you record you will build the song from the ground up, hence starting with the rhythm section first. Often times these tracks are recorded to scratch guitars, vocals, and a click track or a previously produced production track. 
Mixing is the process of combining your multiple tracks to two, your stereo pair. The time it takes to mix a song is really dependant on the song itself (how many tracks it has, etc.). One way to shorten this process is to not leave the engineer to fix every known problem during mix down. 
Mastering is the final step before your CD will be duplicated, and the last opportunity for an engineer to put the final touches on your CD. Some of the things an engineer might do are remove extra time at the beginning and end of the song, remove pops and hiss, compress your stereo track, EQ if necessary, and make all your tracks sound similar in volume so someone playing your CD isn't startled by one song being too loud and not being able to hear the next song. |
