I'm a newbie

Here's how I learnt it in college. Your Basal metabolic rate (BMR) is the amount if calories your body requires to just lie there & run your organs/brain. You'll want to calculate that first. In my case it's about 1430 calories. When we lose weight it's best to keep as much lean mass (muscles) as we can. The more we have the higher our metabolism. I can eat below my bmr, but then I risk my body breaking down greater amounts of lean mass to have enough energy to meet that bmr level to keep my organs running well. Muscles drive our metabolism. They also require a lot more from the body to maintain, versus fat which really requires very little from the body. The body will break down the muscle not only to get energy, but also to lower the demand for energy (lowering the metabolism) so it doesn't require quite as many calories next time. Because fat requires much less to maintain than muscle, your body will not break down too much of it. Itll ficysing more on the items that both use more energy and can be use for energy. Two birds one stone. Setting yourself up for a hard time in the future.
Basically what I'm saying is calculate your BMR and use it as your goal. If you over eat, burn enough calories to get down to the bmr. If you exercise, eat enough calories to hit that bmr. You should still lose weight, and it'll be at a healthy pace. Keep that metabolism going strong! Just make sure your calories burned at the gym are accurate.
I learned about this in both nutrition and physiology classes a few years ago now, and it's worked well so far Hope that helps