What does opens mean in bowling?

Answer 1

Open Bowling means that the lanes are open to the public, because currently there are lanes that are unoccupied by leagues/tournaments.

There is also a term called open used when you do not get a pick up your spare.

= =

An open is also a type of tournament. There are 2 types of tournaments. There is an open where anyone can enter the tournament and there is an invitational where you must qualify one way or another (depending on the tournament) to play in a tournament. Either type can be a pro-am tournament where both professional and amateur bowlers can bowl. There are tournaments that only a professional can enter and some tournaments that only an amateur can enter.