What exactly is the "pins and needles" feeling?

Likely blood flow.: This feeling is likely from the return of blood flow after sitting or resting or being put in such a way as to cut down or stop the circulation of blood to a part of the body, like the foot or arm. The affected area gets numb and feeling can even be partly lost. If it is corrected, and put back to a normal position, the blood flow returns and there are "pins and needles", before normal feeling.