As I understand it, the terms are pretty much interchangeable.
You insert the right needle into a bound-off stitch* (that's the picking up part), wrap the yarn around it and pull it back through the bound-off stitch (that's the knitting part). Leave the new stitch on the right needle and repeat in the next bound-off stitch. The result is a new row of knitted stitches.
In theory you could just pick up the stitches without knitting them, but it would be an awkward maneuver and you'd have to knit them on the next trip across the row anyway.
*Of course you can pick up stitches from any edge, bound-off or not.