on collision: pick/don't pick object

New event>system>on collision (advanced) gives the option "pick object A" or "don't pick".

What is the meaning of pick and don't pick?

"Pick" means that the instance will be selected for actions... "Don't pick" means that the instance won't be picked; instead, the action is carried on all instances of the object.

For example, if you want the instance to bounce on collision, if "pick", only that instance will bounce, if you "don't pick", all instances of the object will bounce even if they aren't colliding.

For example, if you want the instance to bounce on collision, if "pick", only that instance will bounce (...)

And in the Event or Action I could tell the collision-event which instance to pick, for example with a private variable?

Sure.

Thanks.