Agile is a way of working derived from software industry, which is a response to the rapidly changing market expectations.

Key aspect of Agile approach is customer focus achieved by reduction of the time necessary to obtain feedback from the user and an adequate response to the collected information. In practice, this is achieved by delivering the product iteratively in short cycles.

The most popular process framework used by Agile companies is Scrum

Scrum is a process framework based on the PDCA cycle that facilitate iterative product development. The basis for operation is a stable cycle called Sprint, in which the team working on the product plans its work, implements the plan, and then inspects results and plans to improve the process.

Teamwork is the basis of all modern working methods. The interdisciplinary nature of the team is crucial in Agile. Enabling continuous daily cooperation of specialists from various fields allows for quick introduction and verification of complex changes in the product, improves quality and reduces losses related to the transfer of knowledge between departments. At the same time, the team must be small enough to maintain effective communication.

https://hbr.org/1986/01/the-new-new-product-development-game 

Working in the Scrum model in a team, two additional roles are distinguished: Product Owner, who is responsible for the business value of the product and prioritization of work, and the Scrum Master, whose task is to support the team in improving the process.

Iteration (aka Sprint or Cycle) is a time-bounded period of work within which a product is manufactured. Each iteration begins with work planning and ends with its evaluation. The feedback obtained during the product evaluation and work progress at the end of the iteration is used in the next planning and enables both the process improvement and the right scope of work to be adjusted, providing the organization with a continuous learning cycle.

The iterative approach means gradual improvement, modification and reworking of the most important elements or functionalities of the product in accordance with current priorities.

The result of the iteration work is a prototype. A prototype is a physical product, a type of model that allows you to verify the assumptions made when planning iteration. The prototype, especially in the first stages of work, has a very limited set of functionalities, which expands as the work progresses. Modular designs with stable interfaces make it easy to modify prototypes. In order to be able to present a functional prototype at the end of each iteration, the organization must emphasize the time of prototyping. This may involve the use of specific tools, changing the model of cooperation with suppliers and adapting internal processes.

Well-known from the LEAN approach, continuous improvement is a pillar of the Agile approach. The improvements operate around:

• product - continuous adaptation to the changing needs of the user and changes resulting from market dynamics, technology development and acquired information, as well as the evolution of the design to support frequent modifications
• processes - continuous and quick process adaptation based on feedback, transformation of the work model from design phases to a cyclical approach based on functional prototypes, optimizing processes in terms of speed, including supply chains, tooling and certification processes, and automation of repetitive processes, especially in the area of ​​quality assurance.
• organization - Agile is based on the concept of interdisciplinary teams, which have a different communication model than classic organizations based on competence or area silos, improvements that cover such areas as employee allocation, budgeting, work evaluation or competence development systems.