In the old days of Bridge there was a Convention called Strong Jump Overcall.
If an opponent opened 1♦, (for example), and you Overcalled 2♠, you were showing a stronger hand than a simple 1♠ Overcall would have shown.

The problem with that convention is that it doesn't arise very often. Modern players have found a better use for the jump overcall, called the Weak Jump Overcall.

This is one of the easiest Conventions to describe:
A Weak Jump Overcall is exactly like a Weak 2-Bid.
  • 6-card suit with some honors
  • 6-11 points
Even the responses are the same, 2NT being the only forcing response.

No lesson per se, but look at the Weak 2-Bid lesson.