HI, I am student and I want to work with Arduino, I have seen there are a lots of types of Arduino, and I want to know if you can tell me which can I buy to start.
Hope you answer. 
What do you want to do with it?
If you have no specific requirements the Uno is the best starter board because most software and add-ons work with it.
...R
The Uno is the a great start. Basic functions to play with and learn on. Also has a ton of shields that are compatible with it. Have fun.