The following presentation will help you understand these concepts.
Gradient – steep and gentle slopes
It would also be helpful to watch the following short video clip:
http://https://www.google.com/search?q=Calculating+gradient+in+geography+video&oq=Calculating+gradient+in+geography+video&aqs=chrome..69i57.17821j0j1&sourceid=chrome&ie=UTF-8#kpvalbx=_B4