Fleet

A Fleet is an an assemblage of a House's military starships used in combat.

Codex
"Each house ultimately derives its power from the military force it can bring to bear to protect its territory or threaten its rivals. Each house maintains at least one military spacefaring vessel, usually several. In fact, maintaining this fleet is one of the primary economic activities of each house and the part of the general population it controls.

A vassal house is obliged to participate in the military adventures of its master. Thus, while a ruling house might have a small house fleet, they can command a fleet of the combined military vessels of their colony when they need to defend it or answer a call to arms of their leader.

Because military fleets are ragtag collections of ships from many houses, and because each house's ability to maintain and supply ships at particular locations varies wildly, a leader's fleet is not a permanent entity. Instead, a leader may have access to the militaries of strong vassals on one side of their faction, and to a much poorer fleet on another side.

You can see the size of the fleet that you can bring to bear at a particular location by clicking or hovering over a star system on the map. The value shown is the strength of ships you can bring to bear at that location if a battle were to occur this instant, and the maximum strength you could bring to bear when you and your vassals are at full strength.

If the military fleet of a house is damaged, it will gradually be repaired and restored to full strength over time - this is always the primary focus of any house."