Structure not only displays a hierarchy of items, it also allows you to search items based on their relative positions in the hierarchy. The language used to express such queries is called Structured JQL or S-JQL (where JQL stands for Jira Query Language).

Structured JQL queries are available in these places:

Get Started with S-JQL

We recommend starting with the S-JQL Cookbook, which contains a number of common examples that can be used as is or modified to meet your specific needs.

Master S-JQL

For a comprehensive description of the language and structure() JQL function, consult the S-JQL Reference.