"Playing out of Position" (OOP) means that the opponents in the hand are acting after you. So whoever is the first player to act is playing OOP. Preflop, "Under the Gun" is OOP to everyone on the table. The Button is ultimately in position against all other players, but has to act before the Blinds PreFlop. The Blinds, while getting to act second to last and last PreFlop, will be OOP after the Flop if they are still live. Once players see a Flop, relative position will not change among remaining players. In other words if the Small Blind plays after the Flop, he/she will always be OOP to every player in the hand. First to act is OOP to everyone else, second to act is OOP to everyone but first to act, etc.
"On the Bubble" refers to the "money bubble". In any poker tournament, the number of payouts will be "X". As the number of remaining runners in the tournament approaches X, the tournament is "approaching the bubble". The bubble bursts when the last person NOT to cash busts out. You don't want to be the person to finish X+1, the last person to bust without cashing. This is the "Bubble Boy" (or girl).