The mod_deflate module provides the DEFLATE output filter that allows output from your server to be compressed before being sent to the client over the network. Currently mod_deflate is using with newer version of Apache. mod_deflate is the replacement of mod_gzip which was used with older version of Apache. Read: How to enable Gzip...
Read More about How To Enable Gzip Compression Apache on Ubuntu 18.04 & 16.04