STO provides a free ship for each 10 levels advanced up to Rear Admiral. These ships are often referred to by tier, a Lieutenant's vessel is a Tier I, a Lieutenant Commander vessel is a Tier II, etc.
There are three categories of vessel for ranks up to Admiral and specialized vessels at the rank of Admiral. It is possible to purchase each type of ship available to each rank. Players also have the option of purchasing additional ships with either energy credits or dilithium.
Each new rank will reward the player with access to a new vessel.
Star Trek Online provides the player with command of a starship which is to some degree customizable. 3.2.1 Non-playable Klingon Empire Ships.