These costumes can be worn as every day clothing, and also used as swimsuits.
However, if things go really well, the "Invite Home" interaction will appear.
If it's chosen and accepted, the controllable Sim will call a taxicab, and both Sims will get in and go to that Sim's house.
A Sim who is already Downtown can approach another Sim and say "Let's Date" or "Let's Hang Out".
The controllable Sim will be able to use the "Ask About Mood" interaction to determine which motive his or her date wants to fulfill at that moment.
Dating is a romantic activity where two Sims spend their time doing romantic things together.