Pyplot's plotting methods can be applied to either the Pyplot root (pyplot.plot()) or an axes object (axes.plot()).
Calling a plotting function directly on the Pyplot library (pyplot.plot()) creates a default subplot (figure and axes). Calling it on an axes object (axes.plot()) requires that you to have created your own axes object already and puts the graph onto that customized plotting space.
While pyplot.plot() is easy to use, you have more control over your space (and better able to understand interaction with other libraries) if you create an axes object axes.plot().
Axes.plot() returns an axes object. Every axes object has a parent figure object. The axes object contains the methods for plotting, as well as most customization options, while the figure object stores all of the figure-level attributes and allow the plot to output as an image.
If you use pyplot.plot() method and want to start customizing your axes, you can find out the name of the default axes object it created by calling pyplot.gca() to "get current axes."