This file is generally automatically managed, and it has also access via the conan remote command but just in case you might need to change it. It contains information about the known remotes and from which remotes are each package retrieved:

conan-center True
local http://localhost:9300 True

Hello/0.1@demo/testing local

The first section of the file is listing remote-name: remote-url verify_ssl. Adding, removing or changing those lines, will add, remove or change the respective remote. If verify_ssl, conan client will verify the SSL certificates for that remote server.

The second part of the file contains a list of conan-package-reference: remote-name. This is a reference to which remote was that package retrieved from, which will act also as the default for operations on that package.

Be careful when modifying the remotes, as the information of the packages has to remain consistent, e.g. if removing a remote, all package references referencing that remote has to be removed too.