In music, what does "cover" mean?

It means playing a song by someone else, that you altered in some way.

You’re performing a song done before by someone else.

Yes, but other than the original singer or author, isn’t everyone else? Why don’t they use the term “cover”?

A version other than that of the original performer is a cover; but not a performance of a song by a songwriter that has not been performed before. I see your confusion though; I guess it’s called a cover if it was made famous by the original performer. The distinction is not usually made in certain genres such as folk music.

Music Cover is where a music is covered by someone who is not the original composer/artist. It can be done in various way with musical instruments or song cover (where the different singer sing a song not originally theirs).

Instrumental and Extended music could be consider a cover and especially remixes. Now I don’t know the difference between covers and remixes, maybe remix is more electronically tuned.

Congo Square was written by Sonny Landreth, and he recorded it for an album in 1995.
However, Aaron Neville recorded it in 1994. Which is a cover?
What about The Chiffon’s record One Fine Day? Carole King wrote it, but didn’t record/release a version till nearly 10 years later.

@filmfann A case like “Congo Square” IMHO, is a little grey as far as the traditional meaning of cover. However, I would not consider The Chiffons’ version of “One Fine Day” a cover because Carole King was a “studio writer” at the time.

Now her song “You’ve Got A Friend” is a different story. Her recording was released on her album around the same time as a version by James Taylor. In that case I’d consider her version the original and his version the cover.

Sometimes you hear about a “Cover Band”. That is usually a band that has an entire show based on one other group. They play a lot of the music from the original band and almost none of their own.

A “cover band” and a “tribute band” are almost the same thing, except “tribute bands” usually are dedicated to one specific famous band.
Another meaning of “cover” is the fee you pay to get into a show.
But in the Youtube video you posted, the word is referencing the fact she is playing the work of somebody else.
A cover can be done in the exact style of the original, or it can be altered in some way, on purpose, or on accident.

I would consider the genre “tribute band” to be a sub-genre of “cover band”.

Although I’m generally not a fan of tribute bands, I do like Brit Floyd, a Pink Floyd tribute band.

I once played in a cover band that had no name. We were the house band for a bar on Sixth Street in Austin.

^^ “Well, I’ve been to Austin in a band with no name.”

^^deja vu!