Black holes are fascinating celestial objects. They are both simple and complex. A deep understanding of their properties requires knowledge of the general theory of relativity by Einstein. We will not go there. Instead we will consider their basic properties and examples. Starting with the simple definitions we shall progress to black holes that dance about each other.
Suggested Reading: Black Holes Can Dance, Journal of the Washington Academy of Sciences, vol. 97, p.1 2011 by Sethanne Howard. This is available online, no subscription necessary.