How to check the changelog of a package on Linux

When a program or a library is packaged as a Deb or RPM package for distribution, several metadata files are included in the package. One of them is a “changelog” file, which records in reverse chronological order what changes occurred each time the package has been updated. So if you want to find out what changes are made to the package that you are about to install or already installed, you can view the package’s changelog.