Things are usually changing rapidly in an enterprise IT environment. For a variety of reasons, it’s important to understand not only the current state of the architecture, but also previous states, and more importantly: the future state (i.e. the vision the enterprise is driving toward).
This time dimension is typically documented by having a version of the models for each of the important states (e.g. current state, target state, interim states). These are often referred to as as-is or to-be models, but its not uncommon for others terms to be prevalent within an organization.