"Because" and "because of" are quite similar, and they only reveal their differences when used (i.e. in providing a reason for doing something). For example:
1) "Because you did this (action), thats why I did that."= In other words, your actions were the cause of my actions. In this case, it is used as a "conjunction" (a word that links your subject to a verb)
2) " Because of your actions, I did that."= Again, your actions are the cause of my actions. However, in this case it functions as a "preposition", where they appear in front of nouns or verbs.
Other than that, their functions are similar.