matplotlib subplots_adjust - meaning of parameters
These values represent the distance of your subplot from the boundary of the figure. Its value is between 0 &amp; 1. For example, if you set top=1 the upper boundary of your subplot will coincide with the upper boundary of your figure and if you set top=0 the upper boundary of your subplot will coincide with the lower boundary of your figure and the plot will be entirely squashed down. 

It is the percent of figure height and figure width.

A better way to see how this works is to plot a graph and the use the option Configure Subplots, in the window that pops up, to adjust these values. Try this and you will able to appreciate the use of these values in a much better way.