when feeling a pg tummy you can tell the position and presentation of bub.
Position is which way bub is lying, you feel for the spine/back, find out if it is at the front of your tummy, at the side, or at your back, and on your left or right. and from there you know one end has to be a bum and one end a head. Heads are hard, and 'balotable' (i love that word but think i may have spelt it wrong) meaning they move (because they are connected to a neck), bums are soft, and if you try and wiggle them they dont move so easy.
Presentation is which part is down (basically) breech, being bum down (simply there are more than 1 way) and cephalic is head down. there are also transverse lies where bub is lying length ways not up and down.
next time you go to your mw or ob and they feel your tummy ask them to explain what they are feeling for.