A muse is a person or thing that inspires a creative artist, such as a writer or a painter, to produce new and original work.
For example, a singer may find inspiration from a beautiful sunset and write a song about it. Similarly, a poet may be inspired by a loved one and write a heartfelt poem.
Very Simple Definition:
A muse is someone or something that helps artists create new things.
For example, a singer might get ideas for songs from pretty things, like sunsets. Likewise, a poet might write poems about people they love.