The base fleet is the stationary fleet 0 that is always positioned at your homeplanet. You cannot move nor cloak the base fleet, so there is always a target for enemies attacking your system.
You cannot change the attitude of the base fleet, it is always set to defense
Fleets 1 to 3
You can move these fleets and engage other star systems and homeplanets of other players by entering the target coordinates to fly to.
A fleets can consist of ships of 4 different classes. you have 3 fleets in which you can organize your ships. a fleet is only complete if it has ships from all 4 classes.
You need at least one class 4 ship with a warp drive (for example a mothership) in your fleet to travel in deep space. Most class 4 ships can generate a warpfield around your fleet and open a hyperspace gateway through which the fleets travel. When you loose all your warp capable ships in a fleet, this fleet hangs in space and can only return when you send another fleet with another warp-capable ship.
You can set the attitude to 'attack' , 'defense' or you can define your own secret attack-code. All encountering fleets in space that have different attitudes fight against each other. fleets with the same attitude stay in peace. Fleets with 'attack'-attitude always attack all other fleets. your planet always has a defensive attitude, so if you want others to help you they have to put their fleets on defense also, otherwise they would fight against your planet.
A cloaked fleet is invisible to other fleets and cannot fight. you need at least one ship with a cloaking device to cloak your fleet.
Here you can find a list of veteran fleets