Yoda was the head of the Jedi council and a legendary Jedi Master.
He lived for 900 years and in that time helped to train many Jedi, including Obi-Wan Kenobi and Count Dooku.
As the Republic began to fall the tiny Jedi Master had to decide whether Anakin Skywalker could become an apprentice to Obi-Wan Kenobi.
Even though he wasn't completely happy to give permission, Yoda decided Anakin should be trained.
But the young Jedi and his master had to be saved twice on Geonosis after being captured.
First the the clone army, led into battle by Yoda, saved them from execution then Yoda himself had to draw his lightsaber to rescue them from Count Dooku.
Later Yoda was forced into hiding in the Dagobah system, but trained one more Jedi before his death - Luke Skywalker.