When you reflect on your own life, a factor common to many of your memories and learning experiences is their emotional dimension. Despite this being the single most obvious feature of learning, this simple observation cannot be explained by the learning theories we have today. (Where there is an attempt e.g. 'Flashbulb memories', they are treated as the exception rather than the rule. Other explanations citing 'distinctiveness' are patently circular).
As you and I experience the world it is our reactions to stimuli that are encoded. These reactions are affective - by which I mean subtle emotional states. Some of these reactions are innate, some are learned. It's a good system - it allows us to store and process important things and forget the rest.
At a gross, conscious level, we call these reactions 'emotions'. But learning is affective in nature all the way down: beneath the level of consciousness our affective 'micro-reactions' (this is the new term I'd like to use) encode with a sophistication comparable to our visual experience: just as emotions 'happy, excited, angry' compare to 'red, green, blue', so does the sophistication of the affective context compare to the totality of our visual experience.
A blind person might imagine vision as experience of different patches of red, green and blue - but this would be wrong in the same way that 'affective context' is not merely gross emotional reactions - for example it is not a statement about making things 'fun' to make them memorable.
This is why the philosopher Nietzsche wrote 'thoughts are the shadows of our emotions, always simpler, darker, emptier'. We take it as poetic expression, since it is hard to imagine our emotions being literally more complex than - say - the works of William Shakespeare, but this is the founding error that we owe to our rationalist, Cartesian tradition.
It is these 'micro-reactions' to events that are encoded, and we call upon them to reconstruct a story.
The strength of the Affective Context Model is that it offers a single, unified explanation of findings in learning, it explains observations that are currently inexplicable, and it makes accurate predictions in simple, everyday circumstances: for example if I insert the word 'erection' into an otherwise dull string of words, that is the one you will remember. It explains why you forget the repetitive but insignificant event and encode the singular significant one. Why you can't learn some things, and can't help but learn others. Why it matters if you care about a subject at school - or if the teacher cares abut you.