Figure is the object with the highest level in the hierarchy. It corresponds to the entire graphical representation and generally can contain many Axes.
Axes is generally what you mean as plot or chart. Each Axes object belongs to only one Figure, and is characterized by two Artist Axis (three in the three-dimensional case). Also other objects such as the title, the x label and y label belong to this composite artist.
Axis objects that take into account the numerical values to be represented on Axes, define the limits, and manage the ticks (the mark on the axes) and tick labels (the label text represented on each tick). The position of the tick is adjusted by an object called Locator while formatting tick label is regulated by an object called Formatter.