Digital Copies of Retail Games
Sony PSP users can download full digital copies of retail games from the PlayStation Store. These games are exactly the same as the retail box copies of the games, but they are downloaded digitally, directly to the PSP device. The prices of these games vary, with the most expensive digital copies costing 40 dollars (as of 2011). The sizes of these games also vary, ranging from a few hundred megabytes to a gigabyte or more.
PS One Classics
PSP users can also download PS One Classics from the PlayStation Store. These games are digital copies of games that were successful on Sony's original PlayStation console. Because the Sony PlayStation had its games distributed on CD-ROM discs, each PS One Classic is under 700 MB in size. The prices of these games vary, but they usually fall into the five-and-ten dollar range, as of 2011.
PSN Digital Games
PSN digital games are games that were developed specifically for digital distribution on the PlayStation Network and are only available as digital downloads. These games are generally smaller in size than digital copies of full retail games, and their price point is set lower than digital copies of retail games.
PSP Minis
PSP Minis are games that were also developed specifically for the PlayStation Network, but they are significantly smaller in size than their other PSN counterparts. These bite-sized games have a 100 MB size limit, and generally cost somewhere between one dollar and five dollars.