Simply put, cropping is the re-framing of your image, a way to redefine the edges and proportions of what is shown within the frame. Unlike other aspects of photographic composition, which are usually applied as you take a photo, cropping can also happen in post-production, after a photo has already been taken.
While too much cropping can lead to a decrease in image quality or cause a photo to appear awkward or unnatural, thoughtful cropping can be used to:
It isn’t necessary to crop every image, but if used with the right understanding of compositional principles, cropping can become a powerful tool. Furthermore, with the rise of digital media, it is almost inevitable that we will all come across and use images (whether taken by ourselves or others) that could benefit from a thoughtful crop.