The flow in CSS is the logical way in which elements get placed on your screen.
For example, when you turn off the CSS on this page, you see the HTML in its original order.
Padding is invisible space between the edge of the box and its contents, and the background will show through the padding area.
Unfortunately, not everyone's browser will support the spiffy Java Script menu behind that innocent-looking button.
If your browser won't display the menu, just click on the button and you'll be taken to a separate page with the entire menu displayed in clear, non-Java Script HTML.
Inline boxes on the other hand are laid out horizontally.
An inline box will always sit to the right of the box that precedes it, assuming there's enough room in the containing element. They will start to the right of the previous box and fill whatever horizontal space is remaining.