An X-Ray segment encapsulates all the data points for a single component (for example, authorization service) of the distributed application. Segments include system-defined and user-defined data in the form of annotations and are composed of one or more sub-segments that represent remote calls made from the service. For example, when your application makes a call to a database in response to a request, it creates a segment for that request with a sub-segment representing the database call and its result. The sub-segment can contain data such as the query, table used, timestamp, and error status.