A dependency is an external component that is called by your app. It's typically a service called using HTTP, or a database, or a file system. Application Insights measures how long your application waits for dependencies and how often a dependency call fails. You can investigate specific calls, and relate them to requests and exceptions.
Set up dependency monitoring
Partial dependency information is collected automatically by the Application Insights SDK. To get complete data, install the appropriate agent for the host server. Learn more about how to set up application insights here.