(k1 p1 k1) in next st

Can someone explain to me what it means to (k1 p1 k1) in next stitch?

It was preceeded by M1P.

It means just what it says. Knit into the stitch, do not slide it off the needle, purl into the same stitch, do not slide it off the needle, knit into the same stitch - and slide off needle.

wow, really? So I’m knitting three stitches into one? Crazy.

Yep, it makes a double increase.