In poker, the term open describes the very first aggressive action before the flop, i.e., the player opening the action.
For example, you could say something like: it folds to me in the cutoff, and I open to $15. This means that you’re making the very first raise in the hand (2-bet).
This particular term is useful for distinguishing between the first raise and all the actions that happen after. When describing the hand, the person making this initial raise is often referred to as the opener.
