2D stands for two-dimensional and a 2D barcode contains information in both the horizontal and the vertical unlike traditional barcodes which are vertical black and white lines and contain a lot less data. A 2D barcode also physically looks different compared to a traditional linear 1D barcode.
In terms of data capture, a 1D barcode can capture a series of digits, like a serial number but a 2D barcode can capture anywhere up to over 7000 characters so it can contain much more information within the barcode itself.
Traditionally, with a 1D barcode, if you are capturing a serial number or information, you would have to connect back to a server and your device would have to connect back to get any information associated with that serial number. With 2D Barcodes, all the information can be contained within the barcode so it can be anything such as a product name, product color, category, any information you want and you do not need to connect back to a server to collect the data.