Time series data is event data that is recorded and analyzed over time. This document discusses considerations for modeling time series data in MongoDB such as resolution, retention policies, and schema design. It provides examples of different schema designs including embedding data at different granularities like per document, per minute, or per hour. It also discusses use cases for time series data like operational intelligence and monitoring. Overall, the document outlines best practices for modeling, aggregating, analyzing, and scaling time series data in MongoDB.