I need help with "sich"

I often hear a "word" in German sentences, the word is "sich". I do not have a total understanding of what this means and how it is used. I have a dictionary and can read the "definitions", but I don't quite get it. thx.

Disclaimer: I'm not a native German speaker, just a fellow student, so if my answer is faulty in any way, feel free to correct me! :) "Sich" is a reflexive pronoun used when an action reflects back onto the speaker(s). For example: "Er rasiert sich" = He shaves himself, or "Sie freuen sich"=They please (themselves)/They are glad. Since there are a lot of reflexive verbs in German, its probably a good idea to learn when to use "sich"-for instance, "sich benehmen"-to behave (oneself) has a different meaning that simply "benehmen"-to take away. :) Other times, it's used more in an idiomatic sense, when there the verbs aren't reflexive. Example: "Die Welt dreht sich um die Sonne." -The world revolves (itself) around the sun. I am certainly not an expert on this, so if any of this is wrong, correction would be most helpful, indeed. :)