Please don't just rip that label off your new skein of yarn and get started on your project (as tempting as that is)! There's valuable information on that label, and you're going to want it later. So, instead, peel the label off carefully, trying to keep all the print information intact. Then, you might want to clip 6 to 12 inches of the yarn itself and staple or attach it to the label. This way, you will have all of the details about the yarn and its care instructions. You might also want to attach the label to the finished crochet project, especially if it's a gift, so that the recipient will know all about the yarn too and how to properly care for it.
There are no standards for what information must be included on a yarn label, but labels can include some or all of this information (especially those from the large manufacturers): the name of the yarn and the dye lot number; how many yards/meters of yarn is included in the hank or skein; how many ounces/grams are included; the designated weight of the yarn (for example, worsted weight, DK, etc.); the fiber content of the yarn and how best to care for the finished project (for example, hand or machine wash); recommended sizes of knitting needles and crochet hooks to use with the yarn; the number of stitches and rows that should work up using the recommended needles or hook (the "gauge swatch"); where the yarn was manufactured; and, sometimes, recommended patterns for the yarn.