Definition of break even
You can be in profit (+), you can be in loss (-) and you can be break even (+/- 0). Whether it's an evening of poker, a business project, an evening at the casino, when we talk about break even, we mean that with our gains and losses or gains and expenses, we arrive at 0 so, no profit or loss. Sessions break even to poker can be numerous. "I was a loser in my session before I won this gigantic pot; now I'm break even and I'm going to take a break.
The break even games
When we talk about break even, we can also talk about types of games in poker. As a winning player, you will always want to make EV+ games (long term winning games), but sometimes you will make games that will be break even, i.e. have a long term winning expectation of 0. This is usually the case with river bluffs. After analysis, you realize that not doing or bluffing will, in the long run, be a break even game. Whether or not you bluff in this situation will therefore be insignificant to your long term winnings.