What is a stitch in crochet?

I have been crocheting for about 5 years now, and I can pretty much figure out everything I come across, but on this I'm puzzled. I got a free pattern off the internet, and it uses double crochet (dc), single crochet (sc), and a slip stitch (sl st). There are some others too, but in starting the next row it says "St in next 2 dc..." Below the directions is says that St stands for stitch, but which one? I am confused and I'm uming that it stands for either Sc or Sl St and maybe it's a typo. Unless I'm missing something. Is there a stitch that is just called Stitch?