Architecture

Architecture is about looking at a system from a point of view that makes it appear simple, sometimes artificially so. It provides a way of looking at the "conceptual essence" of something without getting bogged down in every detail.

An architectural viewpoint

It has to be simple to understand, to describe, to compare with other viewpoints, and, ultimately, to implement.
The viewpoint might seek a broad approach to a big, sweeping problem. Then again, it might be a thematic idea that can generate a family of similar solutions to a crowd of similar little problems—that is, a design pattern.

Adopting such a viewpoint inevitably limits one's implementation choices. That can be good. If all options are open, ten similar problems in your project might get solved using ten different techniques. That can require up to ten times more work than solving them all with a single technique, outweighing the usually meager benefits of handcrafting each solution. It can take up to ten times as much effort for a new developer to understand how the code works. And when it comes time to change the approach(es), it might take up to ten times as much effort to make that change (since you'd have ten different starting points). So, limiting variation saves time, makes things much easier to understand, and lets you discover and factor out common code much more easily.

When we simplify enough, and in the right way, we wind up with a viewpoint that contains a small number of concepts to think about, each of which has a clear set of responsibilities, relationships, and interactions with the others. It points the way forward on multiple fronts. A viewpoint like that is usually a sign of a successful architecture.