Adding tasks to the backlog
Before development starts, all user stories are added to the product backlog - a list of requirements for a product. Features, bug fixes, all the things needed to successfully deliver a viable product.
Sprinting for the long run
A sprint (or iteration) is the basic unit of development. It usually lasts for a week or two and aims to implement a fixed number of backlog items. The goal of each sprint is to have a system that is integrated and potentially shippable.
At the end of a sprint, the team reviews the sprint to articulate lessons learned and check progress. A new set of backlog items is chosen for the next sprint, and the work continues until the product is ready for the market.
This process increases the quality of the final product, copes with changes, provides better estimates without spending too much time on them, and allows you to be more in control of the project schedule and state.