Backstitch is the outlining. It adds definition to your stitching, gives shape, and can draw attention to particular aspects. Some people hate backstitch or find it tedious, but I enjoy it - I love seeing a project tie together and those weird vague shapes get a form and function. Backstitch is also the easiest stitch - it's just creating lines.
Backstitching should be left until all your other stitches are completed. This will allow it to stand out by sitting over your other stitches. Push your needle up at one, and then down at two. Work your way around your design. Backstitch lines can be straight, diagonal, or cross multiple squares.
Some designs are made up entirely of backstitch, specifically blackwork or designs featuring quotes.
|This design, from the World of Cross Stitch magazine is|
predominately made up of backstitch, with only a few
crosses and beads.
Next post will be about half-stitch, which to me is the last of the three main stitches in cross stitch.