Definition: Ergonomics is the study of people's efficiency in their work environment.
The 5 aspects of Ergonomics are:Safety, Comfort, Easy to use, Productivity/Performance, Aesthetics
A safe product would be one that can be used without harm to the user.
A comfortable product would be one that can be used to help make the user more comfortable, for example, a char that lets the user adjust the height of the arm-rest.
A easy product to use would be one that does not require the user to study the user manuel to use the product. It should be usable with minimal instructions.
A productive product would be one which can be used to enhance the efficiency of the user.
Aesthetics refers to how nicely the product is decorated.