When the Record Label refers to Mixdown and Mastering (M&M) it is referred to a Multi-track M&M. This is the most extensive and precise form of M&M possible. The Artist is recommended (and in case of Firespace Recordings required) to have a Multi-track M&M export available. A brief comparison

:

Multi-track M&M
Non Multi-Track M&M
Very precise control for the M&M engineer on all areas of his craft (Extremely) Limited control for the M&M engineer on all areas of his craft
Low chance of M&M compromises  High chance of M&M compromises
Can work with both dry and wet sounds Can only work with wet sounds
Highest quality possible guranteed High quality is still possible, yet very unlikely
Eligible for a remaster Uneligble for a remaster
Takes longer to process to a final master Fast processing to a final master
Is organized and arranged Is likely disorganized and improper tagged