Ballet has 5 (well, okay, 6) basic ways to position your feet. These positions are labled 1 through 5, with fourth position possessing an open and closed form.

In each of these positions, your feet are supposed to be turned out from your body. Ideally, they are turned out completely, meaning that the line created by your feet is parallel to the line drawn between your shoulders. However, most of us ordinary mortals are not limber enough to perform this feat of feet. If you cannot turn your feet out all the way, simply do so as much as you are able and work on your stretches.

Note: it is entirely possible to force your feet to turn out entirely, but this is a bad idea. If you have to force it, you will actually be twisting your leg at the knee, which, over time, may cause your kneecap to pop off like a bad date. Besides, it is almost impossible to move with any sense of grace while forcing your legs to contort in such a manner, so suck it up and don't be so competative.

In the following bad ASCII art diagrams:
o represents your heel.
- represents your foot.

      --oo--    first position: feet in line, heels together

    --o    o--  second position: feet in line, heels apart

        o--     third position: feet touching, one behind the other
       --o                      overlapping by about half the length

        o--     open fourth position: feet about one foot apart
                                      heels lined up with each other

       o--      closed fourth position: feet about one foot apart
                                        overlapping each other entirely

       o--      fifth position: feet touching, overlapping each other entirely