Stem-changing verbs, also known as "shoe verbs" or "boot verbs," take the same conjugation endings as regular -er verbs, but have two different verb stems depending on the grammatical person the verb is conjugated for.
Listen to J'ai vu maman embrasser le père Noël, the French version of "I Saw Mommy Kissing Santa Claus." They are sung to the same tune, but the lyrics are somewhat different.