Caramelize Onions
Caramelize means to brown the sugar in the ingredient. Onions are high in sugar. Caramelizing is a chemical process in which the sugars decompose under the influence of heat; turning sugars into other complex flavor compounds. Caramelization of onions happens at low heat. At high heat, the onions will burn before they are caramelized. Caramelized Onions are low heat slow 45 minutes minimum. Sweet and tender.

There are two different terms going on about frying onions

1. Sauteed Onions (also called Grilled Onions)
2. Caramelized Onions

Sauteeing is a cooking technique with very high temperature with very little fat while shaking the pan all the time, so they won't overheat and/or stick. To saute is to brown the ingredient by quickly heating that ingredient by vigorously moving in the hot pan (in French, the term saute means "to jump"). So sauteed onions are high heat. Browned and Soft inside still have a bit of an onion bite.

Grilling in this case to grill and to griddle means to cook on top of a flat-top grill as in using a pan on a stove-top. This is a completely separate meaning from grilling over open flames or coals like on a barbecue. This is the sense you hear in the term "grilled cheese sandwich."

Caramelize means to brown the sugar in the ingredient. Caramelizing is a chemical process in which the sugars decompose under the influence of heat; turning sugars into other complex flavor compounds. Caramelization of onions happens at low heat. At high heat, the onions will burn before they are caramelized. Caramelized Onions are low heat slow 45 minutes minimum. Sweet and tender.

Onions are high in sugar, so when sauteed they caramelize some, but caramelized onions are made by a very slow process. During the high temperatures used in sauteeing they go from translucent to burnt without really passing the nice caramelized stage.

[ https://cooking.stackexchange.com/questions/39767/what-is-the-difference-between-saute-and-caramelizing-toppings ]