1. A barcode is an optical, machine-readable representation of data as a sequence of bars and spaces that conform to accepted standards. Linear (1d) barcode standards include UPC, EAN and 128. QR is an example of a 2d barcode standard.
Source: Election Terminology Glossary - Draft, National Institute of Standards and Technology (NIST), https://pages.nist.gov/ElectionGlossary/
2. A barcode is an optical, machine-readable representation of data relating to an object. Barcodes come in a variety of formats including 1D (barcode 39 or 128) and 2D (pdf 417). Barcodes can also be encrypted. Barcoding is a common technique to permit rapid identification of ballots, election materials, and voter records.
Source: Glossary - Introduction to Information Technology for Election Officials, U.S. Election Assistance Commission, https://www.eac.gov/assets/1/28/Glossary_IT-Terms_Managing_Election_Technology.pdf