In technical terms, an API is a computing interface that allows for the creation of applications that can access the features or data of an system, application, or other service. With regards to Milestone, API allows for the integration of various Campus Labs products with the Milestone system so that Open Badging data can be used to leverage assessment across multiple systems. 

When it comes to badges within Milestone, systems such as Chalk & Wire or Engage can be connected with the Milestone system to allow users to provide evidence towards these badges directly through these connected systems. For example, integration can be set up in such a way that a student assessed within Chalk & Wire would be automatically awarded a Badge within Milestone to show their progression towards their goals.