top is a standard cli process monitoring utility. It lists processes and lets you sort them by memory by pressing M or CPU usage by pressing P.
top does not have very good support colors (though they can be enabled by pressing z) and it lacks some of the features similar alternatives like htop have. That being said,
top it is a very advanced tool with a lot of options. It is worth learning how to use
top even if you prefer using htop because of how standard it is. Any random server or computer you encounter will have
top - but the chances of htop being present is fairly slim in comparison.
The top manual page lists a lot of command line options as well as keyboard shortcuts you can use.