Weak Squares?

I have been reading alot latly where they are talking about color square weakness - "whites dark squares are weak" for example. And then they talk about Bishops - well here a picture is worth a thousand words.

 I the above diagram Whites Light squares are considered weak - ok that is completely understandable and easy to grasp. But what I do not understand is - in general what bishop of whites would black look to liquidate - the white one or the dark one?

Is there any good material that you could suggest that would go over the general principles of understanding how to play color square weaknesses?

And as an after thought - what is the importance - if white moves his pawns one square the "weakness" is eliminated or in now on the other color. Seems to me this is what I have read as a "dynamic" weakness (I think) and is only tempory. so is there even any point in building a plan around the dark squares anyway?

Thanks Chess.com Forums - you guys are a very helpful.

this looks like farmers chess.