Answer 1

Block level elements start a new line and get the whole width available.
Inline level elements take the width necessary for their content, and stand in line with previous and next inline elements:

<div>This is a block level element, with <div>another one inside</div></div>
<div>This is another, with an <span>inlined element</span></div>

... will result to:

This is a block level element, with
another one inside
This is another, with an inlined element

Try by yourself and to better see, add css styles to visualize boxes of elements by setting border and/or background ;)