Hello,
I would begin with this KB
https://confluence.atlassian.com/jiracore/blog/2015/07/search-jira-like-a-boss-with-jql
I am not sure what you mean by definitions. Jira does not have hierarchies, Jira has links. You can see links in Issues -> Issue linking and you must be Jira administrator.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.