The w and who commands are similar programs that list all users logged into the Linux, Unix, macOS/BSD computer. Using w, you also get a list of what they are doing https://www.cyberciti.biz/faq/unix-linux-w-command-examples-syntax-usage-2/

If you use who command, you also get the IP numbers or computer names of the terminals they are using https://www.cyberciti.biz/faq/unix-linux-who-command-examples-syntax-usage/