Rank
Ranks show your progression along a factions line of progression and serve as milestones.
Your rank is progressed by buying ships. To buy the next rank of ship, you need to earn enough synergy in one (not all) of the prerequisite ships and then spend the credits to buy it. Your main faction ranks determine which Implants are available to you. Each faction is leveled separately.
Three faction ranks equal one tier. Ranks 1-3 are T1, 4-6 are T2, etc.