The MuleSoft platform from Salesforce allows your customers to connect to a wide variety of APIs, not just those exposed via the Lightning Platform and your application, but ones from other platforms and products available throughout the industry. It contains many connectors so that it is easy for customers to integrate many different solutions together into one set of APIs. It also contains a strong orchestration engine that allows processes to be described with conditional logic and some level of programmatic transformation through its DataWeave scripting language. One of the most powerful features is composing new APIs from several APIs. These APIs can also be consumed from within Apex logic. 

At the time of writing, there is no support for packaging MuleSoft configurations, so this is purely a customer-focused tool. However, you should take the time to understand its value and its various standard connectors in terms of your customers' broader needs regarding integrating your application with other services that already exist within their organization.