FleetsFleets are used to attack and defend planets. In the fleet section, you can do three things. You can send fleets, make fleets and see an overview of your fleets and edit it from that overview. Military in fleets uses population. This population will not pay taxes.
To send fleets, you have to select a fleet and put in the coordinates you want to send it to. If the planet you send the fleet to belongs to you, the fleet will defend it. If it belongs to someone else, the fleet will attack it. If it belongs to noone, the fleet will just move to those coordinates.
For creating a fleet, you have to choose a fleet name, the planet where it will be constructed and how many of each unit you want in that fleet.
The fleet name will be the name the fleet will always have. The planet of construction is the planet the fleet will appear on after it is created. And the units you choose will be the amount of units a fleet has after it is created. You can't have 0 units in a fleet, but you can have 0 units of a specific type in a fleet.
Overview of fleets
The overview will give you information oin the units of a fleet, it's current location, where it is going to and what it will do on the target planet.
When you click on the fleet name, you will go to the edit screen. Here you can add and remove units from a fleet.