A selvedge or selvage is the very edge of knitted or woven fabric. In textiles, it is usually woven differently than the rest of the fabric to create a firm edge. In knitting, a selvedge is made by working the edge stitch(es) a little differently to create a visual or functional element.
From left to right: Selvedge as it looks on the left edge, right edge, right side and wrong side, of stockinette.
Simple Garter Stitch Selvedge
All rows: Knit first and last stitch.
This selvedge isn’t very decorative, but keeps your edges neat and tidy, and also makes it easy to see where your edge stitches are for seams and picking up stitches.
Double Garter Stitch Selvedge
All rows: First 2 sts: Slip 1 kwise through back loop, k1. Last 2 sts: knit.
This selvedge is good for a visible edge. It has a pleasantly pearled texture.
Open Chain Stitch Selvedge
All rows: Slip first stitch pwise. Knit last stitch through back loop.
A simple chain stitch selvedge. You can vary it slightly by knitting the last stitch normally instead of through back loop. This will result in a twisted chain instead of an open one. See the inestimable TechKnitter for more info. The Sweet Oak Shawl and the Crossed Jacket use a chain stitch selvedge.
Chain Edged Double Garter Stitch Selvedge
All rows: First 2 sts: Slip 1 pwise, k1. Last 2 sts: knit.
Like a single chain stitch selvedge, separated from your knitting by a single-stitch column of garter stitch. The Galiano Vest uses this selvedge on the front bands.
The last 3 chain selvedges are slight variations on the Open Chain Stitch Selvedge (3rd image from the top). They are very similar looking. You can find more on them at Vogue Knitting.
“French” Chain Stitch Selvedge
RS rows: Slip first stitch kwise. Knit last stitch.
WS rows: Slip first stitch pwise. Purl last stitch.
“English” Chain Stitch Selvedge
RS rows: Slip first and last stitch kwise.
WS rows: Purl first and last stitch.
“German” Chain Stitch Selvedge
RS rows: Knit the first stitch, slip last stitch pwise wyib.
WS rows: Purl the first stitch, slip las stitch kwise wyif