htop

htop is one of the best interactive system-monitor process-viewer and process-manager.

It is a good alternative to the unix program top. It display a frequently updated list of the processes running on a computer. htop also provides a full list of processes running. htop also supports color and gives visual information about;

• processor,
• swap, and
• memory status

If you do not have htop then you may install it as:

$ sudo apt-get update
$ sudo apt-get install htop

You just type htop to run it....
Ref: https://linuxhint.com/install-htop-ubuntu/

$ htop

You will see something like this: