Frieza, the most powerful being in the universe at his time, was also a cruel ruler who had one desire; to rule the universe. He first went to the planet Vegeta and took it over. When Freiza heard of the legend of the super saiyans, he feared that one day a saiyan would reach that level and overthrow him. So he cowardly destroyed the entire planet. The only saiyans that survived were Raditz, Goku, Vegeta and Nappa, who were all out in space at the time.
When Frieza heard of the Namek's Dragonballs and their power to grant wishes, he went there in hopes of collecting all seven. He succeeded in doing so, but he found out that he needed the password to activate them. He never succeeded in making his wish for immortality.
In a long and gruesome battle, Frieza is destroyed by Goku and his new-found Super Saiyan powers. But the entire planet is destroyed as well.
After a long time, Frieza's body parts are collected and he is re-built with mechanical parts. When he travels with his father, King Cold to Earth to destroy the planet, they are quickly destroyed by a much more powerful Trunks.