What is Instructional Design?

The purpose of any design activity is to devise optimal means to achieve desired ends. - Charles Reigeluth

Here's a four-part definition of instructional design(http://www.umich.edu/~ed626/define.html):

Instructional Design as a Process:
Instructional Design is the systematic development of instructional specifications using learning and instructional theory to ensure the quality of instruction. It is the entire process of analysis of learning needs and goals and the development of a delivery system to meet those needs. It includes development of instructional materials and activities; and tryout and evaluation of all instruction and learner activities.

Instructional Design as a Discipline:
Instructional Design is that branch of knowledge concerned with research and theory about instructional strategies and the process for developing and implementing those strategies.

Instructional Design as a Science:
Instructional design is the science of creating detailed specifications for the development, implementation, evaluation, and maintenance of situations that facilitate the learning of both large and small units of subject matter at all levels of complexity.

Instructional Design as Reality:
Instructional design can start at any point in the design process. Often a glimmer of an idea is developed to give the core of an instruction situation. By the time the entire process is done the designer looks back and she or he checks to see that all parts of the "science" have been taken into account. Then the entire process is written up as if it occurred in a systematic fashion.

There are four major elements in the instructional design process:

• For whom is the program developed? (characteristics of learners or trainees)
• What do you want the learners or trainees to learn or demonstrate? (objectives)
• How is the subject content or skill best learned? (instructional strategies)
• How do you determine the extent to which learning is achieved? (evaluation procedures)
  

(Morrison, G. R., Ross, S. M., & Kemp, J. E. (2004). Designing Effective Instruction (4th edition). New York: John Wiley and Sons, Inc.)

Or, ID can be summarized as a 3-step process:

• Analyze the situation to determine what instruction is necessary and the steps that need to be taken to deliver the instruction.
• Produce and implement the instructional design.
• Evaluate the results of implementing the instructional design.

(Brown, A. & Green, T.D., (2006). The Essentials of Instructional Design: Connecting Fundamental Principles with Process and Practice. Pearson, Merrill/Prentice Hall.)