In a recent post to his site Herberto Graca shares some of his thoughts around packaging and namespacing and how it relates to the overall architecture of your application.
The architecture of a system is the high-level view of that system, the big picture, the system design in broad strokes. The architectural decisions are the structural decisions in the system, the ones that affect the whole code base, the ones that define where everything else will be built on top of.
Amongst other things, architecture is responsible for deciding the systems: components, relationships between components [and] principles guiding the design and evolution of components and relationships.
In other words, these are the design decisions that are more difficult to change as the system evolves, it’s the foundations that give support to feature development.
The post then goes on to talk about "spaghetti" architecture, what makes for a more maintainable codebase and how this impacts the overall structure. He shares a few of the "packaging principles" previously defined by Robert C. Martin and the concept of "screaming architecture" (it should be very clear about how it's structured).