Not a dumb question, BusyStudent! There's so much to learn about with all of this -- and of course, there are both facts and opinions. You'll find a lot of both on 3FC.
Your body burns calories all day and all night, even if you do absolutely nothing -- just to keep your heart beating, your diaphram contracting, your body at a toasty 98.6. Your Basal Metabolic Rate (BMR) refers to the number of calories your body uses in a 24-hour period if you were to stay in bed all day.
Then, everything you do on top of that requires more calories. Even if you never exercise, just walking around your house, standing on line at the supermarket, carrying your laundry up the stairs, you are burning calories (not too many though because I do a TON of laundry and it never made me skinny).
Just google "BMR calculator" and you will get
a ton of hits and lots of good reading. Try a few different calculators to get a sense of your BMR.
Then you can take it a step further and do some calculations that take into account your daily activities and exercise. This helps determine how many calories you burn in an average day. This number can be a good jumping off plan for determining a calorie level that will lead to weight loss.
Keep in mind that all of these numbers of estimates. There are many individual factors that contribute to BMR and to how many calories you burn doing various activities.
Which brings me to the exercise machine. They are notorious for overestimating the number of calories you are actually burning. I use a heart rate monitor but even that I do not trust (mine is pretty bare bones -- maybe the fancier models are more trustworthy).
It takes 3,500 calories to make a pound. So if you want to lose one pound in one week, you need to eat, on average, 500 calories fewer than you burn each day. Some people do this by aiming for exactly 500 each day, while some vary the amount of the deficit each day, averaging 500 over the course of the week.
I think that's all the facts I have on hand, now for the opinion... (assume motherly tone

here): I would suggest that 1,000 calories is too low to start out. You are young and your BMR alone is well over that. Please do some calculators and consider starting higher and seeing how it works over a couple of weeks.
This website includes the line:
Generally, it is inadvisable to ingest fewer calories than your basal metabolic rate. I will admit, I have not really seen that advice elsewhere, but it makes sense. That is the number of calories your body needs to perform all of its basic functions. If it doesn't have enough calories for respiration, circulation, digestion, etc, well, to me that just doesn't sound like a recipe for good health. (turn off motherly tone here

).
Whoo! Sorry so long! I'm not a girl of few words, that's for sure. But now I'm off to do some yoga!