What is the difference between calories from fat and other calories? are all calories treated equal or are do some calories just go toward energy?

Calorie sources: Even though a "calorie is a calorie', depending on where the source of calories are coming from, they can trigger different processes in your body and hence, stimulate fat production. So, for example, a donut of 100 calories would stimulate your pancreas to secrete insulin which is a fat making hormone. Broccoli worth 100 calories would not do so. Hope I clarified it for you.

Calories not equal!: Quality of your calories matters! Refined carbohydrates (white rice, pasta, crackers, cookies, candy) get converted into glucose quickly, which spikes blood sugar & releases insulin, leading to high cholesterol, diabetes, etc. Some forms of calories make you store fat more readily. It's possible that some calories make you gain weight while others don't! (Ref.AARP, 9/2014)