Every Deployment in Humanitec is based on a Deployment Set and is versioned (i.e., it can be recreated at a later point in time). It's probably best to compare Humanitec's approach to versioning with the approach of a Version Control System.
Version Control System Concept
Analogous Concept in Huamnitec
Deployment history in an Environment
Delta generated from the differences between two Deployment Sets
A Delta that can be applied to a Deployment Set