Scrum is a framework and an adaptation from the agile methodology and implies daily stand up meetings and implementation through sprints in the working process. Following the agile methodology, scrum adds an extra step between the Backlog and the implementation phase. This extra step are the Sprints.
Using sprints is a way to cut up major projects into smaller manageable chunks. The team together decides which part of the project to focus on in the coming sprint and then selects the relevant tasks from the backlog. These tasks are added to the sprint and the sprint can begin.
Sprints usually have a fixed time constraint, e.g. 14 days. Retrospectives and sprint planning meetings are also often common practices in project-based companies using scrum.