In windows 7's task manager, we can get a short description of a running process:
Can we get something similar?
One way could be to create a script, which will search the man pages or in the internet for all processes. Is there any better way?
It would be better, if I can get these features in gnome-system-monitor or in KSysGuard
A possible duplicate, but it seems to be cumbersome....
I use Kubuntu 18.04 and 20.04. The process monitor (accessed by Control-Esc) shows me this. Is that what you want. You can then sort by cpu, process etc. 
Some commandline alternatives like cat /proc/{PID}/status are listed in the answers and comments of this question.
Linux doesn't require processes to give a human-readable description, so there is no such thing, sorry.
Your best bet for finding out what a process does would be to simply search for it online (Google etc).
Windows does this by reading properties of the PE that was run.
This is uncommon if at all supported by ELF so no, I wouldn't expect this to be possible without an auxiliary database on Linux. A tool that determines what package the binary belongs to and shows that package's description at best (don't know of any though).
