This pattern is one of four varieties of crocheted snowflakes, which uses the single-crochet stitch in four rounds and calls for counting stitches. And if you're a beginner, learn how to crochet before you start.
As you follow the directions, the loop on the hook does not count as a stitch. The stitch just below it should be the first in your reckoning.
sc = single crochet
sl st = slip stitch
ch = chain
rnd = round
Slip Stitch (sl st)
The sl st is used to join a stitch that was just worked with another one. Insert the hook into a stitch that you want to join with another; catch the yarn, and draw it through all the loops on the hook.