In Photoshop the Cloning Stamp Tool, located on the left side tool bar, allows you to copy one area of an image and use it to paint over another area of an image.

Located below is a beautiful picture of my dog near the lake. Unfortunately she loves to run wild and needs to stay tied up, and I’ve caught her leash in the picture.

Steps 1 and 2: In order to remove the leash from the picture I need to use Photoshops Cloning Stamp Tool and select a brush size from the Brush menu. I’ve chosen one with a hardness of 18%. This helps blur the edges of the brush together when I paint over the leash.
Step 3: After selecting the Clone Stamp Tool and the brush that I wanted,  I move my mouse over to the area that will be used to replace the leash. Option-click (Mac) or Alt-click (Windows) to select the area. The cursor will turn into a target icon while doing this. The area that gets copied is only the size of the brush that you have chosen, however, even if you have a large brush size the target icon will always stay small.
Step 4: Next I move my cursor over to the area that I want to remove. As you are moving around you’ll notice a circle with part of the area you picked up with your target. Placing that over the leash, I can tell what it will look like and then I click and paint over it.
Step 5: Almost there!  It is starting to come along nicely but my cloning is looking a bit chopping because I am only using the same selection on everything. To fix this I select a new area to copy from. (Option-click or Alt-click) to select and go back over a few parts of the leash to smooth things out.
And finally:  Admire the finished product.