Quote Originally Posted by Zippinalong View Post
I think my original statement in my post was obvious: But I don't know the first thing about cassettes and all of those gear ratios (mine is a 11-25T).
So I was looking for a basic explanation of what all those numbers meant.
In simplest terms, the numbers mean how many teeth are on the smallest and largest cogs. The fewer teeth on a cassette cog, the faster you'll go and the harder it will be to pedal. The more teeth, the easier it is to climb hills.

As the range smallest to largest increases, the bigger the jumps between gears will be. This means you sometimes might not have the perfect gear.

Quote Originally Posted by Zippinalong View Post
Also I was asking if they were easy to change out therefore getting an idea if it was something I could do or do I need my LBS to do it. Thanks.
Changing a cassette requires two special tools. However, this is a very basic thing for a shop to do. If you buy the cassette from them (and bring along the wheel), they might change the cassette for you for free.