One of the great "mysteries of life" is explaining what architecture is and is not. :)
The role of architecture is to describe how things are related to each other in a way that addresses one or more customer's needs (whatever those are..ahem) w/in the constraints of the environment and public needs (typically where compliance is described).
The purpose of architecture is to provide understanding, reduce complexity, and enable enterprises to achieve the goals (desired outcomes if you will) for their customers, stakeholders and the public.
Generally, there are about 6 disciplines w/in the scope of architecture (Business, Technical, Application, Implementation, Information, Operational)
"IT architecture" is a term that has been popularized to encompass one or more of the disciplines that are used by IT Departments to provide functional automation services w/in a company.
"Enterprise architecture" focuses on both the intra & extra company assets (logical, physical things).