There are only two types of units, fleets and armies. Only one unit may occupy a province at any given time.
This is a fleet, it is not an army. Think of it as a mix of ships and marines.
Fleets can move in open water. They can also move into and capture coastal provinces. Here, the fleet is in the Gulf of Lyon, and can move into Spain, Marseilles, Piedmont or Tuscany this turn. Or it can move to the Western Mediterranean (wes) or the Tyrrhenian Sea (tys).
Here the fleet moves into Tuscany.
Think of fleets as moving along coasts. They cannot attack overland. Here, the fleet can move north to Piedmont or south to Rome (or else out to sea). It cannot attack Venice overland to the east. To do that it would have to sail around the Italian peninsula.
By the same token, the fleet in Marseilles cannot support the armies in Burgundy or Gascony. However, it can support Piedmont.
This is an army, it is not a fleet.
Armies can move and support any landlocked or coastal provinces. They cannot support fleets at sea.
Fleets can control coasts and project power over long distances. Armies can attack the continent’s interior.