Documentation for JIRA 4.3. Documentation for other versions of JIRA is available too. 
As an extension to JIRA, Atlassian have developed a set of JIRA custom fields, collectively called the "JIRA Toolkit". It can be found online at:
http://confluence.atlassian.com/display/JIRAEXT/JIRA+Toolkit
These custom fields are particularly useful in customer-facing JIRA instances. They were initially developed for use in Atlassian's own JIRA Support installation at http://support.atlassian.com. See the JIRA Toolkit documentation for details.
Overview
Content Tools
Apps
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