Star Wars very well may be the most successful movie franchise of all time. There have been toys, television spin-offs, books, video games, clothes, and so much more around this film series. The original Star Wars movie was released in 1977, The Empire Strikes Back hit the scene in 1980, and Return of the Jedi in 1983. These were technically episodes IV, V, and VI, and episodes I, II, and III were released years later. The final installments, episodes VII, VIII, and IX, began production in the mid to late 2010's, with episode VII, The Force Awakens, being released in late 2015.
In the first movie, a civil war results in the capturing of the rebel leader, Princess Leia. She is in the possession of plans to the Galactic Empire's Death Star, which is a small planet sized weapon that has the capability of destroying entire planets. She manages to stash the plans into the memory banks of R2D2, who ends up on the planet Tatooine, and eventually into the care of Luke Sykwalker, who decides to take him to Obi-Wan Kenobi after coming across a message from the droid meant for Obi-Wan. It is during the meeting with Obi-Wan that Luke learns of his Jedi roots, and Obi-Wan talks Luke, along with Han Solo and others, to join in the rescue of the Princess and to aid in the rebellion against the Emperor as his number 1 (Darth Vadar). In the end, they end up rescuing the Princess, and blowing up the Death Star.
In the second movie, The Empire Strikes Back, three years have past since the Death Star was destroyed. The rebels are living in the Hoth system, and Vadar since out his fleet to destroy them. Everyone escapes Hoth, and Luke sets out to find Jedi Master, Yoda, to begin his training. As Luke trains, Han Solo seeks out help from his old friend, Lando Calrissian, who is actually in forced league with Vadar. Once captured by Vadar, Han is frozen in carbonite and shipped of to Jabba the Hut. During Luke's attempt to rescue everyone, he learns that Darth Vadar is actually his father, and after a fierce battle with Vadar, Luke manages to escape with Lando and Chewbacca, who have plans to rescue Han.
Which is where we start the third movie. In the Return of the Jedi, Luke and the gang set out to rescue Han from Jabba the Hut. Things don't go as planned at first, but eventually the gang is able to rescue Han, save themselves from certain death, and kill Jabba. Luke and the gang find out that the Empire is trying to rebuild the Death Star, so they set out to destroy it. Because the Death Star is being shielded from a forest moon called Endor, the group must enlist the help of the moon's inhabitants, Ewoks, to help destroy the shield in time for the rebels to infiltrate the battle station. In the end, they succeed, and once again the Death Star is destroyed. It is in the final movie that we discover that Princess Leia and Luke are siblings, and Darth Vader redeems himself in the end.
Episodes I, II, and III, are the years before the initial Star Wars movie. They tell the story of how the rebellion came to be, how the Jedi's were nearly all defeated, and how Anakin Skywalker became Darth Vadar. Episodes VII, VIII, and IX will show the years after The Return of the Jedi.