A 1D (linear) code is the most common type of barcode and resembles a series of black and white vertical stripes. The information in the code is organized from left to right and can be read by most barcode scanners. Several variations of 1D barcodes exist, with some able to encode only numbers while others can encode letters or special keyboard characters.
2D barcodes are more complex, as the information within them is represented by both vertical and horizontal patterns, the most common example being rectangular QR codes that can be read by the cameras on most smart phones and mobile devices. 2D barcodes are capable of containing more information than a 1D code while using less space, but require a 2D barcode scanner with imaging capabilities to be read properly.