R2-D2 is your best friend. Since we met him in Episode 4, we have fallen in love with this iconic character.
Artoo first is used as a service droid for the Naboo army. After he quickly saves a ship, he is ranked up. He is sent with the Jedi and Obi-Wan uses Artoo as his personal droid. Throughout the Clone Wars (Episodes II and III), Artoo heads with Obi-Wan and Anakin on adventures and business for the two Jedi Knights. At the end of the clone wars, his memory is erased, except the knowledge of Obi-Wan.
In Episode 4, Princess Leia gives the plans to the Death Star to Artoo, who, with C3PO, runs to Tatoniee, and tries to find Obi-Wan. Artoo is captured by Jawas and sold to Owen Lars, Luke's uncle. R2 leads Luke to Obi-Wan, who takes all three of them to a port on Tatoonie. In that port they find Han Solo who give them a ride to the Death Star.
From 4 to 7, he is on the down low. He is not seen alot.