First off, remove the word Mediocre from your title, You do not need to be putting yourself or your artwork down ever, there are plenty of talent-less assholes, sorry critics
who will try to drag both your work and yourself down, no need to be helping them to do it ever.
Ambient occlusion is a method to approximate how bright light should be shining on any specific part of a surface, based on the light and it's environment.
This is used to add realism.
In computer graphics, ray tracing is a technique for generating an image by tracing the path of light through pixels in an image plane and simulating the effects of its encounters with virtual objects.
To your work, nice work, love the render, great pose, good mirror work.
Constructive comments with praise are always the best way to encourage an artist onward and upward.