slipping the first stitch is a [COLOR=Red]selvage stitch
(where stitch means pattern, (as in garter stitch, stocking knit stitch)[COLOR=Black]
it is just one style of selvage stitch, and its OK, but not the best for seaming --but excellent for raw (unseamed edges) as you might find on a scarf.
many new knitter have a problem with the last stitch in a row being oversized and loose. (and this selvage stitch pattern help hide this)
for edges that are going to be seamed, follow this pattern:
on row 1, work one (knit or purl as pattern calls for), pull yarn snug. work stitch 2 and do the same.
continue across row, normally.
repeat row 1 ‘snugging up’ first and second stitch every row.
as you work a row, you stretch a stich… (by sticking the needle into it)
with each stitch, the stretch get passed to next stitch…(so even tight knitters find it gets easier to knit by end of the row!)
by the last stitch, all this ease created by stretching the stitches works its way into last stitch… and has no where to go! the last stitch swells with the accumulated ease.
if the first (and second) stitch are snug, (and smaller than the other stitches in the row) they can ‘absorb’ the ease, and not get too big.
there are other selvage stitche… one advanced one (again for unfinished/seamed edges) is YO, K2tog.
many newish knitters (and even many advanced knitters!) don’t feel comfortable making a YO as the first stitch…
some patterns (especial fine knits in the european style) call for 2 (yes two!) garter stitches as selvage stitches, and both of these get knit into seam… (in german style sock, they are used in heel, and left visible)