Okay
2 Persons.
Guy
and Girl
Girl: HEY GUY LETS GO ON A DATE?
Guy: OK!
*And now their apparently a couple because they went on a date.*
No that's not how it works you "dummy".
you obviously have never asked someone out before
the term "going out" refers to being together as a couple, if you "ask a girl out" the meaning of that is that you want to literally be boyfriend and girlfriend.
This mostly just applies to younger teen people, but its used both ways with older groups.