Here is another link with a useful, understandable explanation of general
relativity, gravity, and gravitational waves. It appeared in a special
Astronomy magazine article after the January discovery of gravitational
waves. Some of the articles are a number of years old, but I found them
worth reading. The pdf file is 32 MB big so it's too large to send the
article as an attachment. You can download the article from the link and
print it out (which I did) if you prefer to read it at your leisure.