In North America, almost all anchoring ropes are made of Nylon. This is for a number of reasons including its strength and elasticity. After this common factor, you're likely to see two common types of rope: braided and twisted.
There's a number of differences between braided rope and twisted rope, which of most are covered in our article "What's the difference between braided rope and twisted rope?". However, here's the low-down in a couple of sentences:
Braided rope is stronger and is nicer to the hands than twisted rope, but it's a pain to splice. This means if you're using a windlass and chain, you'll probably need to use twisted rope. If you're not using a windlass, go with braided rope.
Simple, non? :)