Intention is the minds direction.

As the mind has learned to give meanings to the objects surrounding it, and based on that made evaluations along the line of ‘good’ and ‘bad’, it begins to make consistent choices. This is how kamma gets accumulated.

When the mind makes a certain decision in one direction or another, it will either create entirely new kamma, or it will modify kamma that has been created in the past.* That is, an intention will either give a new direction to the workings of consciousness or it will modify the way along which consciousness used to work (and thus change conscious experience).

Thus consciousness either learns to “see” new things, or it will change the way it used to “see” particular things.

Intentions may be classified into being of four different kinds: There are strong intentions (viz. a strong will), there are habitual intentions, there are intentions which just follow the nature of a certain sense-impression and there are intentions which are neither.‡ Those we may for convenience sake term as random intentions.†

And, as thus the consciousness of the sensory world changes, so too does the content of the life-continuum change. Hence will whatever has been for, be “taken in”✽ as an image, where it occasionally will manifest, in the form of desires, emotions, or dreams, whenever that life-continuum vibrates.✧

The place of mental processes and kamma in relation to rebirth, I have described in some detail in post on Kamma Paccaya.

* In the second case,  the new kamma will either support some past intention, or it will obstruct, if not entirely annihilate it.

‡ For example, when you were young, you had the strong wish to become a doctor. And based on that wish, you were reading many medicine books and made various efforts to go to university. But then, you got hooked up with a girlfriend and due to that, making money became more important. Thus you developed various habitual intentions, such as a wish to please your girlfriend, the wish to make money, etc. Then, you occasionally watch TV and sometimes seeing some clever advertisement, you develop a wish for the thing advertised. Lastly, you may off and on have some wish coming up in you, which does not possess much strength, nor is it a habitual wish, nor do you remember that it relates to any recent sense-impression. Just some apparently random or arbitrary wish.

† Random here means simply anything which comes not under the above three ways of kamma making

✧Which means, that there are habitual desires, emotions and dreams; desires, emotions and dreams based on strong intentions (will); etc.