Garter stitch is a common basic stitch in knitting which adds texture to your knitting with alternating knit and purl rows. In the image above, garter stitch is used for the border of this washcloth.
Knitting Garter Stitch Flat
If you are knitting flat – back and forth – you would simply knit every single row. Why? Because the backside of the knit stitch is actually the purl stitch. So if you knit each row, you see the backside of every other knit row.
Knitting Garter Stitch in the Round
On the other hand, if you are knitting your project in the round, when you get to the beginning of a new row at your beginning of round marker, then you simply do the opposite of your previous row.