What is the difference between a major 7th chord and a dominant 7th chord in terms of their musical characteristics and how they are used in harmony?

The main difference between a major 7th chord and a dominant 7th chord is the interval between the root note and the 7th note. In a major 7th chord, the 7th note is a half step below the root, creating a smooth and consonant sound. In a dominant 7th chord, the 7th note is a whole step below the root, creating a more tense and dissonant sound. Major 7th chords are often used in jazz and bossa nova music for their dreamy and sophisticated quality, while dominant 7th chords are commonly used in blues and funk music for their bluesy and unresolved sound.