The JIRA User's Guide is for project managers, developers, testers – anyone who uses JIRA. New to JIRA? Start by exploring the JIRA workspace and learning about issues, projects and workflow. Try creating some issues, then search, browse, export or report on them.
The JIRA Administrator's Guide is for people with JIRA administration rights. It will help you set up users and groups, projects, security and email. You may want to customise the look and feel of JIRA, and add your own fields, screens and workflows. Admin tasks such as backup are also covered. You may also find the Knowledge Base, FAQ and JIRA Forum useful.
The JIRA Installation Guide is for people who are installing JIRA for the first time. Check the requirements and supported platforms, then download and install JIRA. Where to next? The JIRA 101 will help you get started, or you may like to import the JIRA Sample Files. If you are using other Atlassian products, take a look at the Integration Guide.
The JIRA Upgrade Guide is for people who are upgrading their instance of JIRA. Start by reading the latest Release Notes and version-specific Upgrade Guide for the version to which you are upgrading, then download JIRA and follow the main Upgrade Guide.
These resources are for software developers who want to create their own plugins for JIRA. Take a look at the Development Hub and the API Documentation. You may also find the JIRA Developers Forum useful.