Barcodes work by encoding information in a series of lines and spaces of varying widths and positions. 

The barcode scanner reads these lines and spaces using a light source and a photosensor, which converts the pattern of lines and spaces into a digital signal that can be decoded by a computer.

There are several types of barcodes, but the most common is the linear or one-dimensional (1D) barcode, which consists of a series of vertical bars and spaces of varying widths. 

The width and position of these bars and spaces represent different characters or numbers, which can be decoded by a computer.

Another type of barcode is the two-dimensional (2D) barcode, which can store more information in a smaller space by using a matrix of dots, squares, or other shapes. 2D barcodes can be read by specialized scanners or by smartphone cameras using a barcode scanning app.

Barcodes are widely used in retail, logistics, and other industries to track inventory, manage supply chains, and improve efficiency.