When you try to explain something to another person, you could end up surprising yourself with how much you actually know about it.
How? Well, the things that are flying around somewhere in your subconcious start bringing themselves to the forefront so that you can use that information. You may have learnt it long ago or even just causally read about it. Things that you don’t even realise you know suddenly turn into words coming out of your mouth.
For a writer it is the same. You have a thought, but this time instead of remembering it for a fleeting moment, you materialise it. Writing takes a thought and creates substance around it, giving it shape and form as it transforms from a thought into a statement.
Writers tend to write because they think. They think about anything and everything. Their job is to turn thoughts into matter that can be productive in some way, shape or form.
To a writer, if it doesn’t eventuate for the thought to ever take form in some way, then the thought may just as well have never been.