Notepad in your case is running in the foreground - you interact with it and when not doing anything it’s in an idle state - not using CPU. You likely have tons of apps running in the background - not interactive as in you dont see or directly use them, but they are eating up CPU time. Pre-built computers are loaded with these apps which offer little to no benefit to you, but gather and send tons of data about your computer and how you use it to Google and other companies that use you as their product. These software makes pay lots of money to computer makers to have them preinstalled and auto-run at startup. You need to identify and remove those apps to regain control of your computer and get it to a calm and cooler state. Windows and every OS forbthat matter have tons of software running in the background which are required and in aggregate will consume a decent amount of CPU and RAM, but typically in negligible amounts so you dont notice any performance impact.
“...they are eating up CPU time”
It seems about half the time I get on the web my PC goes crazy.
And if I stay off the web, I start to get you need to update your anti-virus database messages after about a week.
My PC has become more usable since March, but it still gets big problems.