A chess database is a collection of games for review / study using a database program like Chessbase or SCID vs PC.
Here are three examples of databases that can be downloaded.
KingBase – About 2 million games. pgn or SCID format. KingBase offer a main database with updates by players rated above 2000 (Experts). Also a lite version that are by players above 2200 (Masters).
Chess DB – Search for a players games. pgn format. A great place to look up current players games. Prepare for the strong players in your area. Just type in the name and download a collection of their games.
PGN Mentor – Download individual famous Players, Openings, or Events game collections. pgn format.
As in the case of Chess Engines I recommend placing your Chess Databases in a easy to find common folder for use by more than one program. Example: C:\Chess Databases.
Here is a link to my 1.5 million game Superbase.pgn. Let me know if it works or not. Most games are between two 2200+ opponents, or top players before there were ratings. Very high quality games.