The Clone tool is such a staple of photo editing these days that I assume you are familiar with the concept. But just in case you're new around here, I should point out that the Clone tool lets you "paint" over part of your photo with a section of a different photo. That might not sound practical at first, but imagine that you are Kevin Costner and you just noticed a yacht in the water in the background of one of your scenes in Waterworld. Rather than reshoot the scene, you realize that water looks pretty much the same everywhere. So you grab your Clone tool, tell it to use some water as its source material, and you paint right over the yacht. Now you can finish the movie for under $250 million.

You might use the Clone tool for all sort of reasons, but a common one is eliminating something in a photo that's distracting. It could be a person, a cow, a telephone pole, or some graffiti on a wall. Consider this photo, for example:

Suppose you decided that the big, red sign was distracting, and you'd rather that your photo of Manhattan didn't include it. Sounds like a job for the Clone tool.