What is the meaning of technology "affordances" and "constraints" in terms of education

What is the definition of affordance?

Affordance are properties of technology that facilitate activity and create “possibilities for agentic action” (Hutchby, 2001, p. 444).  The affordance is there, it has always been there, but it needs to be perceived to be realized.  A subsidiary idea is that affordances provide both opportunity and constraints.  The concept of technology educational affordances refers to the properties and the potential of technology that enable the educational interaction between teachers and students needed to carry out their educational plans.  Technology educational affordances are by nature dynamic and therefore should be identified and analyzed in the development of each educational situation.  To read more on a research that took place with the analysis you may follow this link. for a study that took place.  

In the figure above the affordances are push-able, flip-able, and rotate-able. The objects in the environment are buttons, switches and knobs. The action of pushing are for buttons rather than knobs, the constraint on buttons allows it only to be pushed, rotating it will not turn on the light bulb. The light from the bulb is considered feedback which tells us whether our action is successful or not. In the case of the switch and the knob, it tells us which way is on and off. Up or down for the switch, clockwise and counter clockwise for the knob. 

What is the definition of constraints?

Constraints are things that the design of the particular object MUST have and they must be included in the final design.  By creating a list of constraints, it can be used to determine which one will be a developed.  To get teachers to a point of constraints, it’s important to begin on  a common ground.  This article can help you get a better understanding and plenty of examples.  

Constraints limit the affordances and the properties of action associated with them.  To learn more about the students who wrote the contents on affordances and constraints you may follow this link.