Sorry :)
PPA = repository. Each repository has different packages in it, so you'd need to look at the specific unstable tvh you have defined. It seems like it holds nightlies for Wheezy, but I've no idea if it's Pi-suitable (armhf?). If not, you'll need to compile.
dpkg = used to install packages, it's part of the apt framework. It gets called to install a .deb (package) file when you do a sudo-apt get install <package> or a sudo dpkg -I <file>. So, if you just downloaded a .deb file from 'Builds', above, then this is how you could install it if you're desperate ... (and if you were on an Intel system...)
apt-cache policy = will query all defined repositories to tell you what's available. That's the command-line way to test versus going directly to the repository as I just did.