What does it mean by "work 5 stitches"?

The pattern :

[/B]With smaller needles, cast on 36(40-42-48) sts.
[B]Row 1 (RS):[/B] * K1, p1, rep from * to last 2 sts, end k2.
[B]Row 2:[/B] * K1, p1, rep from * across. Rep these 2 rows until piece measures 1" from beg, end on Row 1.
[B]Next Row (WS):[/B] [COLOR=magenta][B]Work 5 sts[/B][/COLOR] and sl these sts onto a holder, p to end – 31(35-37-43) sts. Change to larger needles and work even in St st until piece measures 2" from beg, end on WS.

It means either knit or purl them, depending on the pattern. In this case it might mean to continue in moss stitch, but depending on what the pattern is for, decide how they should be worked.

So I think it might be to purl them, since it says to work in St stitch on the next row?

That’s probably right, since the rest of the row is purled too.

I just read…those 5 stitches are supposed to be for the buttonband, which is here :

[B]Buttonband:[/B] With smaller needles, work 5 sts from left front holder, inc 1 st at inside edge – 6 sts. Work in ribbing as established, working inc st in St st until band, when slightly stretched, fits along left front edge to beg of neck shaping, end on WS, decreasing 1 st at end – 5 sts. Sew band in place, adjusting length if necessary. Place sts on a holder. Place markers on band for 6 buttons, the first 1" from lower edge, the last will be at beg of neckband, and 4 others spaced evenly between. Note: Buttonholes should be worked as rib 2 sts, k2 tog, yo, rib 2 sts.

So is it purl or do I just slip them?

I would do them in the 1x1 ribbing, then slip them onto a stitch holder. You can’t just slip them without doing anything to them or your yarn will be at the end of the row instead of on the 6th st where you need to continue with the rest of the row.