On my Mac, I use iStat Menu to monitor my system. On Linux, there are several tools to do this but I have found Conky to be the most familiar, i.e., looks like iStat Menu.

However, Conky, unlike its Mac counterpart, is quite cryptic to configure. It is a good thing that I use Linux.com's expert guide in configuring it. Try it yourself and believe me, you'd get far more information about your system than most tools available.