Labeling is the display of product information on its container, packaging, or the product itself. The label is one of the most flexible components of the product and may be printed to incorporate variable data (such as a Certilogo code, a barcode, etc.). An additional advantage of using labels is the wide availability of automatic and inexpensive machines for printing and applying them within automated finishing lines.

Encoding:    

Barcodes. Barcodes are an optical machine-readable representation of data. In their original form, they consisted of a series of vertical bars containing variable spacing between them. Since the data is represented in one dimension, they are also known as 1D barcodes or linear barcodes.  They were first used to automate the grocery checkout process.  Both the UPC and EAN standards are implemented with barcodes.  Barcodes are the most used identification technology because they are inexpensive to produce and to read.  Even though they do not contain bars, 2D data representations are still referred to as barcodes and are also known as matrix codes.

Matrix Codes. A 2D barcode is composed of patterns of squares, dots, hexagons and other geometric patterns.  These codes are able to represent more information in a given space than 1D barcodes. This additional storage capacity means that the code doesn't just identify the item, but can also be used to store some of its characteristics. They typically support advanced encoding error checking and correction algorithms – therefore a reader is able to reconstruct of the entire encoded data string even when the symbol has sustained significant damage, something impossible to achieve with linear barcodes.  Furthermore, they can be read more easily even without high printing contrast.  Some common 2D barcode standards are PDF417, Data Matrix, and QR code.
 
PDF417. This stacked linear 2D barcode is used in a variety of applications, primarily transport, identification cards, and inventory management. Along with Data Matrix, this encoding standard can be used to generate postage accepted by the US Postal Service, and it has been adopted by the airline industry for encoding information on paper boarding passes.

ECC200. This standard is one of the most popular of 2D barcodes and widely used in the Western Hemisphere.  It is part of a new traceability drive in many industries, particularly aerospace, defense, automotive and electronic components, where quality control is imperative, available space is limited, there is risk of invasive treatment of the product itself, and a black market exists for the parts.  For industrial engineering purposes, Data Matrix codes can be marked directly onto components, ensuring that only the intended component is identified with the Data Matrix. Data Matrix codes are also common on printed media such as labels and letters. The codes can be applied using various methods, such as ink-jet, laser marking, and electrolytic chemical etching (ECE).

QR codes. The name QR is derived from "Quick Response" because the primary objective of the code's development was high speed decoding.  QR codes are very common in Asia, originally developed in Japan, and initially used for tracking parts in vehicle manufacturing.  In the early 1980s they were adopted in the fashion industry to improve supply chain efficiencies.  QR codes are now used globally in a much broader context, including both commercial tracking applications and convenience-oriented applications especially aimed at mobile phone users.  Also, street artists use them as a new way of creative communication.

Application Methods:

Thermal Transfer Printing. This method melts a coating of adhesive ribbon so that it adheres to the material on which the print is applied. A wide variety of ribbons, such as wax, synthetic, and mixed are available.  It contrasts with direct thermal printing where no ribbon is present and which tend not to last long. Due to its durability, use of thermal transfer is common for barcode labels and in the printing of clothing labels. 

 
Inkjet. In ink jet technology, a high-pressure pump propels liquid ink from a reservoir through a microscopic nozzle, creating a continuous stream of ink droplets.  There are many varieties of inks suited for different surfaces. Due the ease of implementation, its high performance and low cost, inkjet printers are commonly used in packaging.  It is also widely used in pharmaceuticals, food and beverages, and electronics.