I am kind of a math and science ignoramus, but I don't have any idea what "R-squared" is.

That's why we have Google and Wikipedia. Really, if you don't know what it is, and are too lazy too look it up, you can also decide not to answer, and leave an answer for someone who knows what it is.

We don't want to spoon feed people who come here with questions, and expect people asking questions to do some research. But that works both way. "R-squared" is well known enough that it doesn't need explaining -- someone who can answer the question will know what it is; someone who doesn't know what it is, is likely not being able to answer the question.