Cogs and gears

So, I have a new bike! It's not new new, just new to me. I can't promise I'll ride it lots, but I'm pretty sure that unlike my old bike (that I bought when I was about 16) the brakes won't squeal, and the chain won't fall off every single time I try to change gear.

And in preparation for the inevitable questions, it's very hilly round here, so no, I'm not riding it to work/pub etc.