What is the curve below called (if it has a name)? What can you generally infer from such a curve? The line with negative slope is the number of remaining test cases and the line with positive slope is the number of bugs.
It looks like a couple of graphs.
Graphing the number of bugs over time is called defect arrival. If this is a count of total bugs (open, closed, deferred, etc.), this graph is showing a more stable system. Early on in development and test, issues will be found and recorded. Eventually, closer to release, the number of bugs should level out. This graph is saying that between 2/23 and 3/2, few (if any) new bugs were reported against the system. It doesn't say if the bugs have been fixed or not or if the test cases are good enough to find things, but assuming good test coverage, a flat line close to release date is good.
Graphing the number of remaining test cases is the Test Progress S Curve. But this use of remaining test cases appears to be non-typical. Typically, when creating a Test Progress S Curve, you want to track three things: the planned number of test cases, the number of test cases attempted, and the number of test cases completed successfully. Visually represented, the planned test cases would be a line and the attempted and successful would be two bars.
Graphing these two things together also doesn't make much sense. Over time, as you fix bugs, you will likely need to rerun test cases. This isn't shown on this graph. It's one of the reasons why the number of planned test cases to be run in a given test cycle tends to increase over time - you account for new test cases built around new features, but also tests built around discovered bugs.