Crew Skill codex entries provide some basic information about the various crafting and gathering skills. There are 14 crew skill codex entries, and they may be obtained on multiple planets depending on where you first interact with the crew skill vendors. For simplicity I have shown the first available location when progressing the main story line, which is on the faction fleet. You do not have to train in the crew skill to gain the codex entry, you merely need to interact with the crew skill trader. Crew skill codex entries are found in the Crew Skills section of the codex.
Archaeology (Empire) (Republic)
Armormech (Empire) (Republic)
Armstech (Empire) (Republic)
Artifice (Empire) (Republic)
Bioanalysis (Empire) (Republic)
Biochem (Empire) (Republic)
Cybertech (Empire) (Republic)
Diplomacy (Empire) (Republic)
Investigation (Empire) (Republic)
Treasure Hunting (Empire) (Republic)
Underworld Trading (Empire) (Republic)