Thank you Mike (all these Mike's - lol) - I think that explains it very well.
It is important not to attach a product to the idea as yet.
And if we can keep it as simple as possible the better - both what is going on in your brains and also what we output 
For some people's minds it suits them to go into the detail that Mike M has.
Which ever way your mind works: when doing the initial keyword research you do want to put in a simple keyword phrase - this should be
whatever comes to mind first if you where the person looking for say, unusual properties to buy - that would be my keyword phrase I'd first type in:
"unusual properties to buy" (remember my target's the US - so I might add the word US to that phrase. Initially though I'd keep it as simple as possible - later on I can look at States etc.)
Same with the example's Mike also offers above - you'd just type in those phrases: Jewish Internet Dating, Clicker Training etc
When we get into the next stage there is a process of refinement with keywords phrases as Koosa refers to - so stay tuned
Caro