The seed stitch in the United States is a pattern that begins with a knit stitch. Make your knit stitch, then one purl stitch. Alternate knit and purl stitches until the end of the row. In the next row, begin with a purl stitch, and alternate purl and knit stitches until the end of the row. Knit in this alternating pattern until you have finished the work.
In the United Kingdom, the seed stitch is a basic stockinette stitch with occasional purl stitches thrown in as accent stitches. When the work is finished, the purl stitches show up as little "seeds" strewn across the surface of the knitted fabric.
For the United States version of the moss stitch, do two rows of alternating knit and purl stitches, each row beginning with the knit stitch. Make the next two rows alternating purl and knit stitches, beginning with a purl stitch. Continue the work, alternating patterns every two rows, until the work is finished.
The United Kingdom version of the moss stitch is identical to the United States version of the seed stitch. Make your knit stitch, then one purl stitch. Alternate knit and purl stitches until the end of the row. In the next row, begin with a purl stitch, and alternate purl and knit stitches until the end of the row. Knit in this alternating pattern until you have finished the work.