Modern web servers allow website files to be compressed as part of their transfer, often dramatically reducing the Download File Size and Page Load Speed of a page. There are several different compression algorithms used such as GZIP, Deflate and Brotli. Enabling compression can often represent a simple and quick win to performance, and most new web servers will have this enabled by default.
You should ensure that compression is enabled and working effectively on your web server. Sometimes compression may only be partially enabled for particular file types, or using an older compression method, so it is important to understand whether your server is configured as efficiently as possible. This may require the help of a developer to investigate.