After movement is complete, ships which end up on the same position in space can engage in combat. Likewise, ships can attack planets (and their starbases) and vice versa.
The standard combat system in VGA Planets can resolve battles only using pairs of two units (i.e. two ships, or a ship and a planet): if you have multiple ships attacking a common enemy, they'll all fight that enemy one after the other. Your most important tactical utility is battle order, i.e. the order in which your ships fight. You can set that order using friendly codes. PHost implements a similar battle order system as HOST 3.20.
There are a number of fleet combat systems which resolve combat in a completely different way: all ships at once. Those are not part of PHost, and are not described here. There also are a few alternative 1:1 combat systems which basically behave similarily to PHost.
