What is Software Architecture?

The other day I got a nice LinkedIn email from graduate student asking me if architecture can evolve from continuous refactoring. There were a couple of questions about where it worked and where it didn’t, and I started wondering what was really meant by “software architecture”. Well, at the bottom of the email was RUPs definition of software architecture:

“The set of significant decisions about the organization of a software system, the selection of the structural elements and their interfaces by which the system is composed together with their behavior as specified in the collaboration among those elements, the composition of these elements into progressively larger subsystems, the architectural style that guides this organization, these elements and their interfaces, their collaborations, and their composition.”

WTF? What does that mean? What are they trying to say? That architecture is everything? If architecture is the significant decisions, what are the insignificant decisions?