# Segments Segments are collections of contacts that are grouped together based on a set of criteria. Segments are dynamic. This means that as contacts are added to Bird and match the audience criteria, they are automatically added to the audience. The same is true if existing contact profiles are updated and match the audience criteria. If a contact profile is updated and no longer matches the segment criteria, the contact will be automatically removed from the segment. This ensures that your segments are always up-to-date and accurate --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.bird.com/applications/audience/lists-and-segments/concepts/segments.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.