Medium One accepts data as events in JSON format. Each event has an “observed at” time and “event data”. The “observed at” is the timestamp in ISO format in which the event occurred. It is an optional field -- if not specified, then the current timestamp will be used. The “event data” consists of a “tag name” (also known as “key”) and the “value”. When these events are sent in, they are sorted in different data streams. In addition to data streams, each tag is also categorized into data types. In this section, you will learn more about streams, tags, and data types.