ONE DEFINITION of Educational Technology is that it is a systematic, iterative process for designing instruction or training used to improve performance.
Sounds confusing right? Let’s break it down a little…

The mission statement of the SDSU Department of Educational Technology may shed a little light. In part, it says it's purpose is to
...encourage wise use of systems, environments, tools, products, and strategies that can enhance human learning and competence.

If you look up the phrase Educational Technology in a general online or hardcover dictionary or encyclopedia, chances are you won’t find it. If you do, the meaning will probably focus on technology applied to a school setting.
Educational Technology is a hard concept to define because it embraces several disciplines harking back to a time when the systematic study of education was new.
One of those disciplines is Instructional Systems Design, or ISD. During and after World War II, the US military sought a more effective approach to training large numbers of personnel. It employed instructional films and evolved to include a combination of job aids with instructors.
What was different about ISD at the time is that it began with analyzing the learners so that designers could customize instruction to best suit their needs.

ISD also incorporated the idea of a systems approach to developing instruction. It is characterized by an orderly process for gathering and analyzing collective and individual requirements, and by the ability to respond to identified training needs. 

The principal example of Instructional Systems Design is represented by the ADDIE model. Click on the buttons above for more detailed information for each element of ADDIE.

The application of a systems approach to training insures that training programs and the required support materials are continually developed in an effective and efficient manner to match the variety of needs in an rapidly changing environment. 
Another important term associated with Educational Technology is "Performance Technology."

Human Performance Technology (HPT) goes beyond "just" training and instruction. It uses a wide range of interventions drawn from many disciplines including behavioral psychology, instructional systems design, organizational development, and human resources management.
As such, it stresses a rigorous analysis of present and desired levels of performance, identifies the causes for any performance gaps, offers a wide range of solutions with which to improve performance, guides the change management process, and evaluates the results.

Educational Technologist come from many different fields of expertise. The one thing all educational technologists have in common is their love for learning.

Stephanie Walden, SDSU Graduate Student
Walden, S. (2005). Educational Technology.In B. Hoffman (Ed.), Encyclopedia of Educational Technology.