For your example you should think
"to what power should I raise 10 in order to get 1000? there are 3 zeros so it's 3."(or something similar)
but what if I asked you to find log1001? That's right, no idea.
Well, you do know that log1000=3 so log1001 is slightly increased. but that's not accurate. And it doesn't need to be, when it comes to you finding it. Most of the times this is the solution or part of the solution of an equation, which you will give to a calculator and it will I've you back the answer(if you follow maths, physics or engineering you'll learn how).
logx=y means that y is the power of 10 that equals x, thus logx=y is like saying 10^y=x. This is useful when you have an equation, and in the end you get something like e^x=2. By seing it we can understand that you found that the solution x is the number to which e must be raised in order to equal 2. But since that could be just a bit from some lot of equations or relations you'll need to solve, we must have a direct way to express x, and that is the logarith.
1. you don't need to calculate anything, unless it's obvious(lne,log10,log1000 etc)
2.there is no direct way to think it, as the logarithm was made to replace something indirect and bring it to a form we can consider direct, thus mading our lives easier, whithout helping giving a straight answer about what is y=logx(where x is known).
did any of this help?
