what the first person above me wrote is almost correct. However, in spanish, "es" is the conjugated verb of "ser" for if you wanted to say "ella es" or "el es" (he is or she is) Becuase "tu" means "you" in spanish, and the conjugated verb of ser for "tu" is "eres" then the proper definition would be "tu eres muy bonita"

When you eat dirt for the first time and leave your family to build a shack in the woods

tu eres muy bonita" or "tu es muy bonita" actually means "you your very pretty"
the correct way to say it is "usted es muy bonito" means "you are very pretty"

It means you are very beautiful in spanish. Some people use it to holla at spanish girls because its the most spanish words they know.