Simply put, negative space is all of the rest of the space that surrounds your subject. It doesn't have to be totally empty (it can have texture or "things" in it), and how you use it will push the eye of the viewer to rest on your subject, but in a nice way...in a peaceful, restful way. Negative space helps your subject stand out.
I have a horrible, no good, very bad head cold, so I have not been out and about that much. You might say I have negative space in my head. I did take a new image this week, as I visited a shelter/rescue, and you will see that soon, but while commiserating with my 9000th cup of hot tea, I looked back over old images and found that I like using negative space. Here are some examples from the beach two years ago.
In both of these examples, the negative space isn't filled with things. Just water and sand. But that doesn't mean that the negative space cannot be filled with items. How about if we fill it with greenery, for instance, in the scene below of a dog hunting in a field?
And now to see what others have done with their negative space, head to the blog circle. Start with Kim Hollis of BARKography, based out of Charlotte, North Carolina. Have a wonderful weekend!