ps ax

ps - lists currently-running processes

a - lists processes across all users (not just yourself)

x - lists additional processes not ran from terminal (background/daemon processes)

ps -o pid,user,%mem,command ax | sort -b -k3 -r

readable list of user, processes, and PID needed to read in a non-percentage format (see below)

If you want to understand the sort command and flags, this articles does a great job explaining them: https://www.computerhope.com/unix/usort.htm

pmap [PID]

displays memory usage in KB/MB format across all libraries/files associated with the PID