WW - all gears work the same essentially
simply, if you want to go slowly or uphill, you need a "lower gear" - this is done by selecting a smaller ring at the front and a bigger ring at the back. conversely if you want to go faster or downhill, then you need a "bigger gear" which means a bigger ring at the front and a smaller ring at the rear. don't get freaked by numbers of teeth yet, just work on size.