It's all related to where the physical object is located, in relation to the speaker and the listener. This may sound complicated, and at first very unlogical, but when you get the hang of it it's actually very convenient.

Imagine you going into a store and the cleark at the counter ask you what you'd like to buy. You point at the object right infront of you saying "これ" or you might point at an object near the cleark and say "それ" or at something far away from the both of you, then you'd have to use "あれ". It's the same story with　この、その、あの. As easy as that

You never put a noun in front of the -re form of the word. It is used when saying things like "This is ____". When using the -no form, you put a word in front of it, such as another poster said, "pen"... so it's like saying "This pen is ______".

He didn't ask the difference between こ〜・そ〜・あ〜・ど〜. He asked the difference between 〜の・〜れ.

haha xD
my apologies
i totally replied to this while i was basically half asleep (it was..... like 5am my time >.>")
and..... i can't write in hiragana... since i have no japanese input =.=
so yeaaa... bear w/ me? xD

How can you not have kana input in this day? XP, Vista, OSX Tiger on up, and many Linuces all have kana input built in.