Look at the first 30 bytes of the file (open it in Notepad, Notepad++ or another simple text viewer). There's usually some kind of tag or extension name in there. Both SQLite 2 and SQLite 3 have a very clear message: SQLite format 3 for SQLite 3 (obviously) and This file contains an SQLite 2.1 database for SQLite 2. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.