If you're snacking on olives, the pits aren't much of a problem. If you're cooking with the olives, however, you'll want to remove the pits so no one bites down too hard and hurts a tooth. Kalamata olives used in recipes are often chopped or sliced, too, so the pit has got to go.
Some cherry-size olives can be pitted with a cherry pitter. If you don't have one or if the olives are the wrong size, use this method to pit an olive:
Tip: Some olives, such as Cerignola olives, are very difficult to pit. Serve these types of olives as appetizers, keeping a bowl handy for discarding the pits as guests bite away the olive flesh. Always warn guests when serving unpitted olives.