double pointed needles (often called DPNs) are exactly what they sound like. They are needles with points at either end. They usually come in sets of 4 instead fo pairs and are used for circular knitting, particular smaller items like gloves or sleeves for a jumper.
You only actually knit with two needles at a time, just like with regular flat knitting. that meens there are 3 needles with stitches on and one you are usiong to move the stitches if that makes sense. I have yet to try it myslef but will have to when my hat has decreased enough that i cant knit on my circular needle. I think it will be abit fidly at first, but once i have gotten used to the extra needles being ther it should be fine.
Dont be scared of DPNs, but i would say maybe try a circulr needle for kntting int he round if you can, just to get used to having a tube instead of flat knitting first.