A DITA info-type file is synonymous with topic or DITA file. A topic file is a specific kind info-type file used to store topic content.
Topic content can be formatted in standard or specialized ways depending on something called “into-type class”. From the base info-type topic, specialized info-types are built using methods that allow inheritance and polymorphism to establish a new sub-class of information. Some examples of these sub-classes of topic are concept, reference and task. This info-type distinction is important because it provides control over how information is structured for creation, storage, reuse, and repurposed (i.e. the final deliverable). Another important aspect of this distinction is to inform the consumer of the information just what the information being provided is, and how it is being used to describe the subject idea.