What kind of lever is a teeter-totter?

In order for the lever to be in effect, there has to be one of a number of factors. If a heavier person is closer to the bar (fulcrum), than a lighter person, then we have a first class lever. A second class lever would be if someone is moving the end of the board from closer to the bar. The third class lever would be someone between the bar and the end, being lifted by someone else at the far end.

Normally, teeter totters aren't being used as levers.i dont get it !