Plotinus is usually called the Founder of Neo Platonism and what that means is that in this philosophical circle, he was founding a kind of renewed attempt to understand the thought of Plato which however they were combining with the thought of other philosophers, including Aristotle, the Stoics and Pythagoreans and so on.

This is in a way the most important thing about soul is that it's a kind of principle which mediates between the universal intellect and the material world.

Unlike later Neo-Platonists, Plotinus says that our souls are always connected to the universal intellect and that we never really fall away.

We do each have an intellect but there's a universal intellect which is the same for everybody, as it were. And this single intellect is grasping the platonic forms.

The idea is that to grasp an idea like equality or justice, you can't look at the equal and just or unjust things in the world around you, you have to somehow ascend to or maybe remember some kind of idea of equality and justice and this would be a Platonic form, and it would be different from the things that partake in the form.

There's going to be this realm of Platonic forms and then there's going to be this single mind, the 'nous', which grasps them.

Soul puts the determination or forms or images of forms, into matter.