Scrum is one of the most popular set of practices, called a "framework", of Agile.
The key of this practice is the creating of multidiscplinary teams that are commissioned to create something together. This team is called a "scrum" in reference to a rugby scrum.
Each team has someone who is responsible for managing it, a "scrum master", and someone who represents the needs of the customer, a "product owner".
The teams set about to solve a problem or create a solution through a series of short bursts of very focused development, called a "sprint". These sprints, typically two weeks in length, then build to a final release of a solution, called an "epic".
The key to the success of these types of Agile frameworks is that these sprint create Learning Cycles that allows the team members to reflect and adjust, based on deeper understanding of their challenge and adjusting customer needs.