What the <br> 's fonction, and <p> too

Answer 1

Br will just break the line and it may appear that it is working like p tag because it also begin from new line . But you can't give any property with br tag but using p tag you can give property's to the matter inside it .
By the way p is block level tag
And br is inline level tag.

Answer 2

You can google that ,also go through Html course