top command, which is a counterpart of the Task Manager in Windows, will show a list of running programs and how much CPU these programs are using. Monitoring system resource usage is very useful and will help you, especially if you are able to terminate programs that are using too much system resource.
qwill quit the top command.
cSorts by CPU processing time. The order is from largest to smallest.
mSorts processes by memory usage from largest to smallest.