Where the seed stitch is created by alternating the knit/purl stitch pattern every single row, the moss stitch is created by alternating the knit/purl stitch pattern every two rows instead. So the moss stitch is basically a lengthened version of the seed stitch.
Moss stitch is reversible and is one of my favourite patterns in terms of appearance.
You will first need to cast on an odd number of stitches.
Quick side note: Although the moss stitch can be worked over an even number of stitches, I am writing the instructions here for creating a symmetrical pattern, which requires you to cast on an uneven number of stitches.
Elsewhere on this website I have written the symmetrical version of the pattern for the double seed stitch too. Please don't be confused if you see slightly different patterns for moss stitch and double seed stitch on other websites; the different versions create the same pattern but may not be totally symmetrical.
You'll only probably notice this version of moss stitch is symmetrical if you look closely, but I like everything as neat as possible :)
Once the stitches have been cast on, you will need this pattern:
Rows 1 and 4: knit 1 *purl 1, knit 1; Repeat from * to the end of the row.
Rows 2 and 3: purl 1 *knit 1, purl 1; Repeat from * to the end of the row.
Repeat rows 1-4
With this pattern, everything is symmetrical both widthways and lengthways.
Photo showing the texture of moss stitch, by Jessica Spengler.