For the Structural Bio Enthusiast: Torsion Angles

In structural biology, I have come across the term torsion angle many a times. But I never understood the precise meaning of it until today! The motivation to learn about it came from Dr. Xian-Jun's blog: Torsion Angle
Dr. Xian-Jun had given a detailed description of how to calculate it, though he had taken for advantage that someone reading it will know what a torsion angle is - I did not know! A quick google search yielded some informative links. The summary of my learning is as follows: In the newman projection it is the angle between the bond that is nearer to you and the bond that is farther from you. A more clear explanation is given at IUPAC