Why is it important for a business to know their break–even point?

Could you also provide an example? I am trying to understand this better for accounting class

Well they have to know for the selling of product. If they are selling less product then the cost they won't make money.

Two examples:
Fixed Cost (FC) = $2 million
Variable Cost (VC) = $1/unit
Unit Selling price = $2
Expected sales = 1 million

So $1 million profit on the unit, but then the FC are factored in and they actually lost $1 million.

Second example:
FC = $5 million
VC = $8/unit
Unit Selling Price = $10
Expected Sales = 10 million

So in this scenario, despite the fact the selling price is only 20% higher then the VC, they sales are much higher and the company can expect to make $15 million because of the high sales covering the FC.

This is a really really simplified example but I hope it helped.