apt-get update is a command used to update the system packages from the repository.
Ping is a command use to determine if a remote location is reachable
netstat is a command use to print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.
wget stands for “web get”. It is a command-line utility which downloads files over a network.
locate command finds files by name
gzip is a command used to compress one or more files. Here I compressed cat.txt
gunzip is a command that decompress files. So what we did for gzip it added cat.txt.gz, so we use gunzip to decompress it and back to cat.txt
tar is a command use to archivie files. So I created cat.txt.tar
zip program is used to package and compress files. And unzip command lists, extracts, and tests compressed files in a ZIP archive.