As I've been browsing around the Ubuntu forums and general intetnets, I have seen mentioned PPA's and Repositries. I assume PPA and a Respositiry is the same thing really? but am unsure. Either way, I get how they are used for the apt-get install etc to install packages and apps etc.
What I don't know, is how do you trust them? I don't want to go around adding randomd repositries that may contain malicious codes and the likes, but sometimes its likely that the repositires that I have dont have the apps I'm looking for at the time and stuff. But I don't want to just add some random repositry off the internet.
I'm very particular and rather paranoid when it comes to downloading information from sources I have never used before, seem a little shady, or have VERY little public mention.