You can click on the various tabs on the activity monitor window to see the different ways that the applications and services are utilizing the CPU on your Mac or MacBook. Keep in mind that you can only view the information in the activity monitor. If you want to stop an application from running in the background, you will have to do it manually or use the force quit option.
Now, there are many third-party developers who claim to have applications that can help you see and optimize the CPU usage. Such applications are not necessary, as the CPU usage is optimized by the MacOS platform, but even then, if you want to try out such applications on your computer, make sure you check that the developer and the product is genuine. Do not fall for cheap tricks or false promotions.
