Explaining mitosis and meiosis?

i understand the concept of them both, but i do not understand where they happen? i've looked up the answers to this question on yahoo answers and just on the net and loads of people have given some LONG essay. and also on wikipedia i dont understand, its too wishy-washy. could someone just tell me simply the main areas in which mitosis occurs, and the main areas in which meiosis occurs? maaaaaaaany thanks xxx