Simplify the following text for a Grade 6 native English-speaking person.
Original: A major and minor scale sharing the same key signature are said to be in a relative relationship . The relative minor of a particular major key , or the relative major of a minor key , is the key which has the same key signature but a different tonic ; this is as opposed to parallel minor or major , which shares the same tonic .
Simplified: When a piece of music is in a major key , the relative minor means the minor key which has the same key signature .