Status bar information

Hello, sorry if this question is very stupid, but nevertheless
I haven't found answer to it.

So, what is displayed in the status bar, particularly for the gif
images?
I see there size in pixels, size on disk, then some percentage,
and some relation.

What means those percents and relation.
I'm asking because I have two .gif files with identical number
of pixels, but they are displayed differently( different size and
height/width ratio ) on the screen.

Why does it happen?

Thanks in advance,
	Alexander Grigorievskiy