2-Track meaning one stereo file (finished mixdown) which is the most common way to get your masters done.
The individual mastering and summing of up to 8 stems. This is very common in the hip-hop scene, where vocals are treated separately from the instrumental.
The complete mix down of a song. All tracks are treated individually and effects are being added.
The complete package. The complete mix down of a song with 2 track mastering.