Correlation between potential energy and torque

[wjdgone]

In class while learning about electromagnetism, I was given the following two equations:
U=-μ⋅B
τ=μ×B
where μ=IA
First of all, what does μ stand for?
How should I interpret the relationship between potential energy (U) and torque? Can someone explain this in terms of μ and B?

 

[BvU]

Oh boy, did you fall asleep during the first part of the class on magnetic moment ?