Re: How was Epicsnaps made?
If you're a beginner, and want to understand how it works, then I'd start off by trying to do it yourself. Scripts like Gallery2/3 are pretty complicated, and if you've not done much programming before, the source-code can be very over-whelming - you probably wouldn't learn an awful lot by looking at it without a bit of previous experience.
The site probably uses a database to store information about each picture - title, post date, tags, and filename. The image its self is unlikely to be stored in the Database, it's probably just the location of the image on the server that is stored.