ESDAO

During a game you can form ad-hoc teams with other players. When doing this you gain visibility of each other's game data including all commands and scans. When attacking the same hex your ships combine to attack the hex, rather than attacking each other first, with the larger attacker leading.

You ask players to team up from their profile panel. They'll get a message prompting them to either accept or decline your invitation.

Once a player accepts your team request, their map data will appear on your map and vice versa. Hexes will have a white dot in their top left to signify that you are seeing info about that hex as a team mate has shared it with you.

The players tab in the sidebar groups players by their team sharing status towards you. Alliances are rarely black and white, for example take this listing from a game called p3a-577 - it's a web of alliances.

You can stop teaming up with other players whenever you like from their profile panel.

There is no other formal structure to teams, like time periods for example, and you can still attack each other. They are also only between 2 players, if you want to create a team of more than 2 then all potential members need to go through the setup process with each other.