The Forest Moon of Endor is usually just referred to as simply Endor but actually, Endor is a large gas giant which you don't see. The Forest Moon of Endor is where the shield generator for the second generation Death star's of the Galactic Empire is located. Only by destroying the shield generator can a second team lauch an attack directly on the Death Star.
The planet is a lush and fertile land which is predominately forest with a few desert areas. The planet appeared in three films, the other films being Battle for Endor and Caravan of Courage but those two films were nowhere near as successful as Return of the Jedi. The planet also featured in the cartoon series Ewoks.
The Empire chose the moon of Endor because it is wooded and that there aren't any native intelligent life forms, the only life forms are the Ewoks, small furry creatures. The Ewoks are as hated as Jar Jar Binks and are blamed for the second half of the film being a let down.
On the planet are Imperial Scouts, similar to Stormtroopers but they have a different mask and weapon. The Scouts are experts at riding bikes which zip through the forest.
The shield generator is a giant radar dish that protects both the planet and the Death Star from outside interference. The management of the first Death Star such as Grand Moff Tarkin felt that one wasn't needed. Tarkin wasn't aware that Galen Erso, a lead engineer on the project had inserted the weakness into the design.
When they landed on the planet, they were discovered by Imperial scouts and the group ended up being split into different groups. Princess Leia befriended Wicket, an Ewok who took her back to his home. The other members of the group got caught up in a net and taken to the Ewok village to be eaten but was saved by Princess Leia and C-3PO pretending to be some sort of God on account of his yellow shell.
The main entrance was too heavily guarded so the team launched a raid on the back entrance to the base which they believed was not heavily guarded. Palpatine envisaged the battle and expected what might happen although he didn't figure on the bravery of the Ewoks. The entrance looked empty but it was a ruse by the Imperial forces to capture the rebels. The Ewoks started the ensuing battle. Once the shield generator was blown up, the battle up in space started.
The Rebel Alliance fleet arrived at the Moon of Endor but because the shield was still up, there was a stand-off until the shield went down.
The scenes for the moon of Endor were filmed in the Redwood National Park, California, an area in the north of the state close to Oregon. The park is famous for its tall trees. The area was also used for the scenes in the two Ewok movies that followed after Star Wars VI - Return of the Jedi