EA, as the name states, is the architecture that is the integrated blueprint of the enterprise. It, simply put, describes the enterprise from the many angles that serve its various stakeholders.
Hence, EA, as an architecture, is to be employed to
* simplify the enterprise
* operation improvement,
* cost reduction
* align of technology operation to the business wants
* align of the enterprise components evolution to strategy
* analyse business models
* create an an enterprise wide transformation project portfolio
* guide decisions and investment
In more general terms, EA is employed to ease complexity and change management.
The EA may be asked to do strategy but only for IT but this not necessarily an EA task.
The purpose of an EA framework is to enable the delivery of the EA, that is the architecture of the enterprise, rather than solving the problems of the enterprise.
Once the architect delivers a proper EA framework and EA, he succeeds, more or less, to make own self redundant.
EA is successful if it delivers the integrated EA architecture with views for most of its stakeholders (for example top management, finance, IT development, Quality improvement etc) enabling them to achieve their own work objectives in alignment with the enterprise strategy.
If the EA team engages only in policing efforts around the enterprise, without delivering a reference EA, then the EA team failed. The EA blueprint should be used by stakeholders, as much as possible, without the engagement of the architects. The architects are not the factotum of the enterprise.
But the definition of the EA states more than its purpose. It has to answer the What then other W like questions such as Why, Who, How...
It denotes the EA practice that should collaborate and coordinate the many other activities in an enterprise to discover, design and implement the EA and the enterprise target state.
EA also means the EA team that manages the enterprise.
And the EA body of knowledge, the discipline that could be studied and taught.
PS: "The Enterprise Architecture Matters blog" book is soon to be published on Kindle. It consists of all the posts and articles, organised in categories for ease of use, I published in the last seven years or so. About 500 pages of everything you want to know about EA.