O.K. Valium is for anxiety. It's a bit like the regular Xanax (not controlled release). There is a high possibility for addiction with Valium, so it makes sense that your dad might take it in excess. Valium is not an anti-depressant though. It's actually a depressant, a tranquilizer, a downer. I'm sure that it would calm a panic attack, but there are better, less potent and addictivethings out there.
Most well known drugs have websites. I think that the web is probably the only way to research the meds, unless you go to a library and check medical journal articles or newspaper databases to pull old articles about the drugs. To learn about the most common class of anti-anxiety meds, you might try doing a google search for "SSRI" or "selective serotonin reuptake inhibitor." You'll probably get a combination of informative websites about how they work, some positive websites, and some negative websites. There is a substantial contingent of people who simply "don't believe in" medication, so you may read about that too.