html - Difference between these selectors -

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• why spaces used separate things in css 3 answers

is there difference between these selectors?

div.demo , div .demo

div#demo , div #demo

does select same element?

div.demo{some code} div .demo{some code} 

yes, there is.

div.demo match div class demo

<div class="demo"> 

div .demo class demo inside div:

<div>   <span class="demo"> </div> 

same id selector #.