What exactly is attraction and why are/aren't we attracted against the odds?

I have at least one reader who takes an interest in these things, so I thought I might touch upon attraction. What is it? How reliable is it? Can it come and go?
There are lots of aspects to the question 'what is attraction', not least something which has puzzled me for years: how come you can think a woman is good-looking, i.e. 'attractive', and yet not feel attracted to her? And how come you can feel immensely attracted to a woman, so much that jumping into bed immediately wouldn't be soon enough, yet you don't at all think her good-looking and, well, attractive? It really is puzzling.
I find all sorts of things about a woman attractive: a voice, a way of smiling, hips, shoulders, a way of walking, a manner. And, conversely, there are quite a few things which can turn me off - just read the above list. Sometimes, you can find a woman immenselyb attractive, and then she will do something such as laugh - and that laught is such a turn-off, you wonder where your senses were.
I find intelligence in a woman attactive - not a turn-on - and I do mean intelligence, independent thought, not the ability flawlessly to regurgitate something by someone else. (NB For me a sure guide that someone is not particularly bright, or at least rather less bright than they fondly think they are, is if they use that deathless phrase - and believe it - when talking about themselves: 'Intelligent people like us.' Irrespective of the implied flattery - that is, you, the listener, are included in the group of 'intelligent people' - you almost always - no, always - find that the boast never actually stacks up, and you are obliged to ready yourself for a long, long litany of intellectual cliche.
Being attracted, and then no longer being attracted (and we are here talking physcial attraction throughout), is thoroughly disconerting but it does happen, and it can lead to some embarrassing situations.
Then there is the odd sensation of being vastly attracted - and wanting quite badly to do something about it - to someone you really don't like. Strange.
One danger worth mentioning, which many couples often discover rather late in the day and to their costs, is that attraction does not say anything about compatibility. If we are attracted to someone and look about for the nearest bed, couch or even grass knoll under a shade tree, the only thing we can say with any certainty is that we are attracted to that person. It says nothing - although we often think it does - about a glorious future together till death us do part. Yet I wonder how many people have mistaken attraction for such eternal love? Far too many I should imagine. Not that I am any wiser on that matter than anyone else. It is always so difficult to take your own advice.
A joke to see you on your way, which is, at least tenuously, linked to attraction:

Q. What is the difference between a fox and a dog?

A. About 10 Barcardi breezers.

Boom, boom.