Cloudflare Apps is a way of installing web plugins - or Apps - adding a wide range of functionality onto websites, without any coding or technical effort required.
More information about developing apps for Cloudflare can be found here: https://www.cloudflare.com/apps/ or check out the apps available for install in your control panel by clicking on the Apps section in the menu bar.
Most apps available in the Cloudflare app store are created by 3rd party developers. Cloudflare will attempt to provide basic support for those application when possible, but requests for extended support or feature enhancements are best directed to the developer(s) who created the apps themselves.
For questions about using the Cloudflare API please go here.