Process Explorer is an advanced Windows Task Manager replacement.
Hope this clears up the Babylonian linguistic confusion brought about by the two programme names which sound so similar, although the programmes serve different purposes.
If you wish to monitor a particular programme in order to find out which files it will use (read/write) and which regkeys it will use (read/write/delete), which access right problems it may encounter etc pp, then in the past you would have very likely used
Now you can do all this using Process Monitor.
If, however, you wish to monitor system resources, kill and relaunch processes then Process Explorer will be the right choice.