Files, permissions, processes, networking, packages and disks: the Linux commands you actually use, with syntax and examples, and the ip and ss tools that replaced ifconfig and netstat.
Linux commands often have long lists of options they support, many of which are single-letter mnemonics. These can be tricky ...
Linux has over 1,000 commands on a basic service. When you migrate to the desktop, that number grows. For example, in /usr/bin on Pop!_OS there are 1,615 commands, and in /usr/sbin, there are 609.