Home to Yoda during his final years, Dagobah was a swamp-covered planet -- a forgotten world where the wizened Jedi Master could escape the notice of Imperial forces. Characterized by its bog-like conditions and fetid wetlands, the murky and humid quagmire was undeveloped, with no signs of technology. Though it lacked civilization, the planet was teeming with life -- from its dense, jungle undergrowth to its diverse animal population. Home to a number of fairly common reptilian and amphibious creatures, Dagobah also boasted an indigenous population of much more massive -- and mysterious -- lifeforms.
Yoda spent the final years of his life on Dagobah, eking out a simple existence in a mud hut, and contemplating the nature of the living Force.
A vision of Obi-Wan Kenobi sent Luke Skywalker to the Dagobah system to seek out the wisdom of Yoda. The thick jungle proved the perfect training ground for the Jedi apprentice.
R2-D2 did not agree with Luke's assessment that Dagobah was probably perfectly safe for droids. The little astromech was swallowed and spit out by a massive swamp creature, and was encrusted with muck for his entire stay on the bog planet.
The spirit of Obi-Wan appeared to Luke Skywalker during his Jedi training on Dagobah. It was on Dagobah that Obi-Wan confirmed the truth to Luke about his father, Anakin, and his sister, Leia.
A sudden storm sent Luke's X-wing starfighter crashing into a lagoon on Dagobah, where it settled on shifting mud for a time before completely submerging. With the power of the Force, Yoda was able to lift the waterlogged ship from the swamp.