Confluence has a wide range of features on its own, but you can also extend those features with add-ons, and by integrating Confluence with other applications. Integrating with Jira can really take your Confluence experience to the next level by improving the way your teams communicate and collaborate, track vital work, and plan and release new products.
If there's an extra piece of functionality you need, the Atlassian Marketplace is the place to look for useful Confluence add-ons (or add-ons for other Atlassian products). Whether you need to create diagrams, like the ones you can create with Gliffy, or you want to make awesome mockups and wireframes with Balsamiq, there are heaps of great add-ons in the marketplace. You may even find a really useful add-on you never knew you needed, but now can't live without.