Picking up stitches long the edge is useful in a number of applications. Picking up stitches between the edge stitch and the next stitch gives you a beautifully clean finish.
PU Stitches between edge and next stitch
Phrasing Version One: Pick up stitches by putting the tip of the right needle from front to back in between the edge and next stitch. Pick up stitches by wrapping or picking yarn as if to knit and bring the loop through the fabric to the right needle on the right side.
Phrasing Version Two:From the RS, at the beginning of the row, use right needle to PU a new stitch between the edge and next stitch along edge of neckline shaping; at the end of the row, PU a new stitch onto right needle as at beginning.
This technique is used to pick up stitches in many different applications. PU stitches is used to pick up for bands: front, neckline, other trims, and to allow knitting in another direction. This is the most general technique which creates a selvage stitch.