Let's define what is 'Architecture' in software context.
Architecture is a dyscipline and kind of Art, but it's also 'thing', certain quality of all systems. But also that, on which architect's work is focused.
Software Architecture consists of set of decisions regarding structure of software systems, such as:
* system's structural elements choice, and their interfaces,
* behavior of such element's collaboration and cooperation,
* organization of such structural and behavioral elements into larger subsystems,
* architectonic style, that affects this structure's shape.
(TODO: learn and elaborate following)
Software architecture also regards:
* limits and compromises regarding economical and technical restrictions,