I'm always looking for simple definitions of enterprise architecture. A reasonable explanation popped up in my Google alerts feed this evening, offered by Daniel Manoli of Computerworld:
Some areas of networking, such as satellite communications, actually involve rocket science. Building an enterprise architecture, however, is not rocket science. Its goal is to create a unified IT environment of standardised hardware and software systems across an entity, with tight links to the business side of the organisation....
With an enterprise architecture, a company creates a map of its IT assets and business processes, and a set of governing principles that support the business strategy and how it can be expressed through IT. The enterprise architecture specifies equipment, protocol and interface standards; IT strategies; projects needed to bring about the architecture and achieve the target state, and a development/deployment plan.
He adds some sage advice that I'll second: "The key to successful EA is to keep it simple, stupid".