What are the health benefits of "healthy fat"? I used to think fat meant more calories/more weight gain. Is peanut butter a healthy fat?

Satiety. Most people like to eat some fat because it provides flavor and makes us feel full. Saturated fats like in meat and dairy products cause LDL (bad) cholesterol to increase and arteries to get clogged. Unsaturated fats like in nuts, peanut butter, and oils like olive, canola, and peanut, don't increase LDL cholesterol but do increase HDL (good) cholesterol. Just be aware that fat has more calories.