What does it mean to slip a marker?

In the pattern I'm on, I placed markers, then continued to knit to the end of the round. Now on the next round, I'm supposed to knit to the first marker, slip the marker, then purl. Does that mean to move the marker vertically to the row I'm on now?

The marker should have gone around the needle. If you don't have an 'official' marker, you can just tie a loop of yarn around the needle where they call for a marker. When it comes to slipping it, you just move it from one needle to the other.

On occasion, a particular stitch needs to be marked, but in this case they want the marker on the needle.

Slip marker means slip the marker off of the left needle and on to the right needle.

Oh thanks---I had clipped them into the stitches instead of on the needle! Oops!