Knitting directions

Being fairly new to knitting, I don’t understand what the following means: Work as est to 3 sts before for side, ssk, k1, slip marker.

Thanks!

You work across as you have been until there are 3 stitches left on the left needle. Work a slip, slip, knit decrease and then knit the final stitch.

ssk decrease found here: http://www.knittinghelp.com/video/play/slip-slip-knit-english