Trying To Learn More!

That has really good info, but I should have mentioned I meant the modern ones (but checking now, coinfacts doesn't have much in that regard either!) :) I'm still deciding to collect modern silver $1, there are some that are really nice, 2006 Old Mint, 2001 Buffalo, but then you have to get all the olymipic ones which would break me..

As to asking questions. Somewhere I read this and it sums up your asking questions.
The more I know about something, the more I know that I did not know as much as I thought I knew that I know.
Or
The more you ask, the more you learn and the more you learn, the more you realize how little you knew, so in order to not find out how dumb you are, don't ask.

Now that you did ask, I would say a key date is a date where you need a key to unlock something that was locked with a key.

For real, what metalman said. You will be surprized at how some coins are difficult to find and they are not considered key coins at all.