The App Catalog section is where you can configure Application Catalog Settings, define the Access Request Policies, and the New Application Request Policies. 

App Catalog: General Settings Tab

This tab configures what to show in the catalog by editing attributes. 

Read the Applications Catalog Settings article. 

App Catalog: Access Request Policies Tab

This tab configures what will happen when employees request access to apps in the catalog.

Read the Application Catalog - How to Automate "Request Access" Process article. 

App Catalog: New Application Request Policies Tab

This tab configures what will happen when employees request new apps that are not yet in use by your organization.

Read the Application Catalog - How to automate new application requests article.