Scrum: In the scrum, a sprint is a basic unit of development. Each sprint is followed by a planning meeting, where the tasks for the sprint are identified and estimated. During each sprint, the team creates finished portion of a product
Agile: In Agile, each iteration involves a team working through a full software development cycle, including planning, design, coding, requirement analysis, unit testing, and acceptance testing when a product is demonstrated to stakeholders
In simple words, Agile is the practice and scrum is the process to following this practice.