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If you are new to playing guitar and are just starting to look up popular songs, there is a good chance you’ve run across a phrase like “capo on 5.” A capo is a commonly used tool for guitar players that allows them to change key on the fly. If you see a song that requires a capo, that does not mean that you cannot play that song without one, but if you play it as written then it will be in a lower key than the original song. It is also possible to play songs that use capos in the original key without a capo, but this would require transposing the song, which requires some musical theory knowledge.
https://playguitarnotes.com/accessories/what-is-a-guitar-capo/