The main difference between a frittata and a quiche is that quiches typically have a crust. That means that they can support slightly runnier fillings since the filling does not have to stand up on its own. There are crustless quiches that are very similar to frittatas—however, these are usually baked in the oven rather than cooked primarily on a stovetop. As for frittatas vs. omelets, a frittata is generally larger and serves 4-6 people, while an omelet generally serves only 1 person. In addition, a frittata takes up the entire pan to cook, forming a circle when done, that is then cut into triangles to serve. Omelets are more free-form, and are cooked differently. For an omelet, you generally start by adding whisked eggs to a pan and cooking, then adding filling on one side before folding one side of the omelet over the other side. Unlike a frittata, the fillings are not usually interspersed through the omelet itself.