The UML User Guide and Reference Manual discuss two sets of views: architectural views and UML views.

Architectural views are used to identify five interlocking viewpoints, or vantage points, from which to document a software-intensive system. These are a well established, proven set of views based on the 4+1 Architectural View Model by Philippe Krutchen.

The UML views are used to identify useful subsets of UML modelling constructs that can represent one aspect of a system. The division into different UML views is somewhat arbitrary on the part of the UML authors, but they hope it is intuitive.

This diagram illustrates the relationship between UML Views and 4+1 Architecture views (given in brackets):

Architectural Views
Capturing a system’s architecture

As such architectural views and UML views serve different purposes when modelling systems.