The Draft
The Draft has two basic definitions: 1) A character option in multiple versions of Traveller that allow a last-ditch attempt at a "career", outside of becoming a drifter.[1][2] 2) The in-universe Draft, or any minor Draft[3]
Draft Results
Draftees tend to be filtered (randomly) into one of six military careers:
1) Navy (any)
2) Army (any)
3) Marine (any)
4) Merchant (merchant marine)
5) Scout (any)
6) Agent (law enforcement)
Other Drafts
Vargr
In the Vargr Extents, the Draft results are quite different.[4] Armies are always looking for new recruits, while merchant marines have been swallowed up by the Navy and other, less reputable occupations.[5]
1-3) Army
4) Marines
5) Navy
6) Law Enforcement
Notes
It is stated in Classic and Mongoose 2e that characters may typically only enter the Draft once in their lifetime unless otherwise stated.