I will give ANYONE, best answer if you explain this to me?

It's just the way the system was set up. Someone, at some point, decided to name the notes that way. If you actually think about it, there are an infinite number of tones between each note. There are, for example, sounds you can make between an A and an A# (I know because I seem to sing that note all the time when I'm trying to sing an A!). They could have just numbered each half step 1 - 13 instead of using letters at all, but someone decided to use those letters and set it up the way it is.