How to explain mathematical curves.

I found this in one of the blogs. Here's the link to the blog http://theguabancexblog.blogspot.com

1. Explain the shape of the graph.

Its curvy, with a higher bit at the end and a rather aesthetically pleasing slope downwards towards a pretty flat strait bit. The actual graph itself consists of 2 strait lines meeting at the lower left hard corner of the graph and moving away at a 90 angle. Each line has an arrow head on the end.