Each tag has various elements that it can use to further refine how it is shaped and positioned. At this point of your learning you should be looking into the attributes of each of the elements. w3c has an excellent list of attributes for each tag. Go through each one and find out first hand by doing, what each attribute is all about. You will find that in this case, all of these attributes work hand in hand to display the division as desired.
Oh and look up z-index while you're at it.
Don't be afraid to experiment.