What Riss said is correct, but I thought I might add something. Sometimes it is called knitting what "presents" (not the gift kind of present, the other one
). You work the stitch as what it looks like. If it is the flat side of the work, right under the needle as it is facing you, you are looking at a stitch that is a knit, so you knit it. If the little bump part is right below the needle, it is a purl, so you purl it.