Heat is a form of energy, but it’s certainly not the only one; there are so many I won’t bother you with a list. In any complex system — an automobile engine, the human body, planet Earth — energy is constantly changing from one form into another, so if some object has energy (and it always does), sooner or later that energy will distribute itself among the various available forms. Since one of those is heat, in general terms when you gain energy you’ll end up with more heat, when you lose energy, there’s less of it to go around and that means less can be heat.
Another important form of energy is electromagnetic waves. It’s a fancy science term but in at least one form it’s something we’re all familiar with: light. More generically we can call it radiation.
Open Mind 