What is launchpad in apt-get error messages?

Question

when I do sudo apt-get update I get these errors,

Err http://ppa.launchpad.net trusty/main amd64 Packages 404  Not Found
Err http://ppa.launchpad.net trusty/main i386 Packages  404  Not Found
W: Failed to fetch http://ppa.launchpad.net/adilson/experimental/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found
W: Failed to fetch http://ppa.launchpad.net/adilson/experimental/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.

I have no idea what launchpad is. what this error is? what this error points to?

How can I remove this error?

Thanks.

Answer 1

The OP reported in a comment that this problem was solved by instructions provided in saiarcot895's comment, which said:

@John: Delete the files that mention adilson and experimental. I don't remember the exact formatting of the names, so I can't give you a file name here.

In short, the problem here was solved by removing .list files from /etc/apt/sources.list.d.

^{This may be a duplicate of How can I fix a 404 Error when using a PPA or updating my package lists?, though that appears currently to be under dispute.}