In spite of the fact that we've made great strides in engineering technology, management of engineering projects has been slow to evolve to meet the needs of the customer. Businesses are driven by time to market and innovation like they never have been before. Which business will deliver value to the customer the fastest and thus gain market share. This is the focus of Agile.
Agile is a mindset that capitalizes on the knowledge of engineers to produce value rapidly. Instead of producing non-value added items such as documentation or studies, Agile focuses on releasing tangible business value rapidly and using the knowledge to quickly respond to current climates of change. Instead of producing a product over the course of years, the product is incrementally produced over time to meet the customer needs in the moment. After all, if you develop over the course of years, then you deliver what the customer wanted years ago.
Agile is a mindset that has been traditionally applied to software although it is growing into the hardware realm with great success. It's main tenants are that we value responding to change, people and relationships, customer interaction, and an actual working product. These principles may sound like common sense, but that hasn't been the case in traditional development. Compare them to following a plan rather than adapting, no matter how bad. Or maybe we value processes over people. Some developers never interact with a customer to determine their real needs. In the worse case, a working product is never produced at the expense of comprehensive documentation.
Agile helps people think about using these principles to deliver value. They apply it with practices such as Scrum, Kanban, paired programming, Continuous Integration, Test Driven Development, and others. Companies that apply these new methods of management are seeing fruits that far outpace their alternative methods. They are seeing a competitive advantage. They are seeing value.