Feature Type

The concept of a Feature Type is used to name and describe set of vector data (known as a Feature Collection). This terminology comes from the Web Feature Server specification; which is a web service that publishes the definition of a feature types; along with vector data that matches that type.

A Feature Type consists of several interesting parts:

a type name - this is the name of the content; it could be as informal as the filename that contains the content; or it could be a formal name provided the organization making the information available.
attribute types; describe the information recorded about the features
a default geometry; this is the geometry that is drawn on the map (unless you are more specific)

You can think of a feature collection as being the data; and the feature type as being a description of that data.