GS1 application barcode identifiers (AIs) are numerical prefixes that help specify the meaning and format of data encoded in barcodes, aiding in their interpretation. They are essential for various GS1 barcode standards and support both human-readable information and machine processing. There are over a hundred AIs, each with specific uses, formats, and examples, such as the Serial Shipping Container Code (SSCC) and Global Trade Item Number (GTIN).