If you're talking about the Culinary Triangle, it involves three types of cooking, boiling, roasting, and smoking, commonly done to meat.
changed
The chemical composition of foods is changed during cooking.
small green triangle
The food Darkens
reached the maximum level allowed.
The power in the Bermuda triangle is electricity, gasoline, cooking oil, some wind turbines and solar power.
first line indent marker.
It indicates a slow moving vehicle.
A useable taxiway
All three interior angles of a spherical triangle may be right angles.
It indicates a problem with the vehicle. Flat tire etc.
A right-pointing triangle ▶︎ is commonly used to indicate a submenu.