edit. Just noticed the update stating migration to a p25 system. So, better get a p25 scanner to future proof yourself.
Welcome to Radioreference.
Did you see this quote from the 2nd post above?
Sure, the BC125AT is a good beginners scanner but you'll no sooner learn how to program it and get all comfortable with it, and then your area will start switching over to digital. That scanner is analog only.
You were asking what P25 is. Take a look here and read up on it ~~~>
APCO Project 25 - The RadioReference Wiki.
And this link here~~~>
Main Page - The RadioReference Wiki, will help you learn about the different aspects of scanners and what is involved with them, from basic scanning questions right up to information on digital scanners.
There are many links there that will help you with questions that you might have in regards to this great hobby.
You should read up on what's out there and what you might like in a scanner.
Good Luck