Editing photography - Website

When editing some of my images, I decided to crop them out so they had no background. When researching editing techniques I came across a helpful website to help me when cropping which is less time consuming than using the 'Paint' software. The website allows you to get rid of the unwanted parts of the image by shading it red, and the wanted areas green. The unwanted parts would then disappear leaving only what you wanted. The website I used was http://clippingmagic.com/

Here is an image of how you use it: