Shrek is a large, green, lovable ogre that wants nothing more than to live in peace and quiet in his swamp. However, when he's befriended by a donkey and forced to rescue a princess in order to save his swamp, he ends up doing what he thought he could never do, fall in love.
In Shrek 2, Shrek marries his love, Princess Fiona, and returns back from his honeymoon to get to know the family. Once there, Fiona's supposed-to-be husband, Prince Charming, along with his fairy godmother are stirring up trouble.
In Shrek 3, after his father-in-law dies, Shrek is next in line to the thrown. He either has to to the throne himself or find the next-of-kin, the King's nephew, Arthur Pendragon.