Although Dagobah is probably not Yoda`s birth world, this planet is where Yoda seeks solace when the Emperor takes control of the Republic. The planet is one large swamp with creatures swimming around in the water and no intelligent life except for Yoda. Luke Skywalker is instructed by Obi-Wan Kenobi to visit Dagobah for Jedi training, Luke obeys the advice.
The film appears in episodes V and VI only when Luke visits Yoda for Jedi training. The planet is a dark planet, with not much sunlight getting through the undergrowth and darkness.
Dagobah is probably the inspiration for the World of Warcraft zone Swamp of Sorrows. Luke leaves Dagobah to rescue his friends he believes are in danger but it is a trap set by Darth Vader. After Luke Skywalker and Princess Leia Organa has rescued Han Solo from Jabba, the Hutt, Luke returns to Dagobah for further training but it is cut short when Yoda dies.