https://medium.com/free-code-camp/the-most-important-css-concept-to-learn-8e929c944a19   

Check following at the end of link:-   
NOTE: As pointed out by Paul McCann in the comment section, the paragraph above is an over simplification. Have a look at what he says.   
[I really expected an !important pun somewhere (!important by the way has a value of 1,0,0,0,0)]   