The past form of the verb dream. This is the more common and preferred form. The alternative spelling dreamt is also correct but less widely used.
He dreamed his symphony would take the world of music by storm
The past form of the verb dream. This form is correct, but less common than dreamed. It is used especially in British English, although there too it is less common than dreamed.
There is a famous Zen story about a man who dreamt he was a butterfly