It is not a set of practices. There is no silver bullet, golden nugget or platinum compass. The agile manifesto is a set of values and principles that have learning, excellence and collaboration baked into their very heart. They will not prescribe how to deliver valuable, delightful software, they will not explain whether TDD or BDD is best. They do not insist that you use a product backlog, user stories, story points, iterations, stand ups, demos, code reviews, peer programming or continuous integration.
“Agile” adoption will not help you if you do not understand this. It will not help you if you are conflating “scrum” with “agile”. It will not help you if you do not truly understand what it is you’re getting yourself into.
… agile is defined by its principles rather than specific practices.
The agile manifesto is what it is: guiding principles and values that empower you to make your OWN decisions on how to deliver valuable software (or anything for that matter).