How many units (and how much revenue) you need to cover your costs.
Break-even units equal fixed costs divided by the contribution margin per unit, where contribution margin is price minus variable cost. At that number of units, total revenue exactly covers fixed plus variable costs.
It is how much each sale contributes toward covering fixed costs, that is the price minus the per-unit variable cost. If it is zero or negative, you can never break even at that price.
It is the sales income at the break-even point (break-even units times price), the minimum turnover you need before the product becomes profitable.