In this video, the professor is illustrating a Nyquist plot for the function G(s)H(s):

At the 25:37 mark, he draws a contour around the origin and says:

At the 25:37 mark, he draws a contour around the origin and says:
I understand his previous explanation about why the phase should transition from -180 to 180 degrees via 0. However, I'm having trouble understanding the concept of asymptotes and how that relates to the drawing he is making."The contour angle approaches the origin asymptotically, moving toward -180 degrees as it gets closer, and as it moves away, it approaches asymptotically to plus 180 degrees."