Readers are used to read a variety of lines or codes. There are several different types of readers out there.
Readers: A barcode reader "reads" a barcode (a symbol made up of a cluster lines of different heights and widths) and retrieves the corresponding data related to that specific barcode. Barcode readers use the reflection of light or some sort of imaging technology to process or "unlock" the code. We most commonly see barcodes used in stores. You bring the shirt you want to buy to the register and a barcode reader scans the object. Once the barcode is scanned the inventory name of the item and its price magically appears on the register. The barcode reader matches each item's specific barcode with the corresponding data. Barcode readers can be fixed (like connected to a register), portable or integrated (like the one you can install on your mobile phone).
Reference: Morely, Deborah, and Charles Parker. Understanding Computers Today and Tomorrow. Boston: Course Technology, 2011. Print.