Back Stitch is worked from right to left and is great for creating solid lines. It helps to shorten the stitch length when using this stitch (and other linear stitches) to outline curved lines. You can also use this stitch to fill a shape and then we call it Brick Stitch. It's also a great stitch for lettering.
Start a stitch length away from the beginning of your line. Come up at A, down at B, the start of your line. Then up a stitch length away at C, and back down at D (same hole as A). Up again at E and then down at F (same hole as C).
Whipped Back Stitch. To whip your back stitch come up at A, the beginning of your line. Then weave under and over EVERY stitch until you reach the end of the line. Bring your needle down at B and anchor.