Total revenue is the result of multiplying quantity times price. Elasticity measures what happens to revenue when price changes. For example, on any given night the Toronto Maple Leafs sell 18,000 tickets, at an average price of $100, to yield total revenue of $1.8 million per game. But what if the Leafs increased their average price, would they sell as many tickets? And would they sell at least enough to make total revenue per game greater than it was?
If after the price increase total revenue per game is higher than $1.8 million, the price of a Leaf ticket is said to be inelastic (insensitive to price). If they sell fewer tickets, to the point where total revenue is less than $1.8 million per game, the price is called elastic (sensitive to price).
This is why essential industries like water and power are always regulated. Their volumes are too insensitive to price.