2 questions - one about collusion the other about a definition

[bobbyi]

As others have said, opening means being the first one to voluntarily put money into the pot. It is a pretty old term; for example, five card draw was sometimes played "jacks or better to open" which means the first person to enter the pot needs at least a pair of jacks (seems like a stupid rule to me, but I don't understand draw).

Technically you can open-raise or open-limp. However, it is fairly common on twoplustwo for people to just say "open" when they mean open-raise; since a lot of people never open-limp, the raising is sort of implied. For example, someone could start out a description of a hand by saying "it folds to me in the cutoff and I open with AK" which generally implies a raise.

"Open-fold" is actually a different term. It usually refers to folding in a situation where there is no bet you. For example, you are first to act on the river and you just throw your cards in the muck rather than betting or checking since you missed your draw. Obviously this is not a tactically sound play.