Power Down

Can any of my lovely fellow Steemians (Is that the right term?) explain to me how this Power Down thing works?

I did a bit of research into it and it seem that powering down steem, means loosing that Steem Power a little, but the power gets turned into Steem / Steem Dollars instead?

Only, I also read something about waiting 1-2 years?

Still feel like I'm new to this cryptocurrency world... I'm trying to learn! :P