Bar codes are machine-readable symbols used to represent data in a visual, scannable format. Typically appearing as lines of varying widths, bar codes are commonly used in retail and manufacturing for tracking inventory, managing point of sale transactions, and speeding up checkout processes. They can store information such as product numbers, serial numbers, and batch numbers. Bar codes can be scanned using optical scanners called bar code readers. The technology enhances efficiency and accuracy in data handling across numerous industries.