Custom Apps enable you to pull data from a 3rd party source into the customer sidebar. Ideally, it would display information that adds context about the customer and your relationship; such as account level/plan, order history, how long they have been a customer or anything else that's important to your business.
This example App (image to the right) pulls information from a custom CRM, which includes contextual information about the customer: company name (including a link), how long they've been a customer, user role, plan name and lifetime value.
Two Kinds of Custom Apps
Your custom App can take shape in one of two formats: Dynamic or Static. Dynamic Apps are more powerful, but require a bit more savvy on the developer side. You provide an endpoint URL for Help Scout to call when the page is loaded, which loads a JSON message with your data for rendering. The example above is a Dynamic App.
If Dynamic Apps sound like Greek to you, try a Static App. All you do is provide HTML that you would like rendered on the page. In most cases it would be a URL that uses one of the variables (like the customer's email address) to do a customer account lookup.