This data type has no identifiable structure. In turn, structured data is generally available in tabular form.
Unsupervised learning comprises a set of statistical tools intended for use in an environment in which we only have (or use) one set of input variables on a set of n observations/instances. In this sense, we are not interested in prediction, because we do not have an associated response variable.
URL (uniform resource locator)
This refers to a text string that specifies where a resource can be found on the internet.
Validation or Test
The results verification phase of creating a model through a machine learning algorithm. That is, a test of whether a newly created trained model generalizes or behaves well when considering new data.