Amazon (US) PSN Store
PA PSN Friends List
How do the stores work?
Each region basically has their own, separate store. SCEA run the American stores, SCEE run the European, Middle Eastern, Indian, African and Oceanian (all of which are usually shortened to PAL) stores and SCEJA run the Japanese, Hong Kong and other East Asian stores. It's honestly a bit of a mess, as some games get released in one region and then take months to come to other regions. The good news is that you can create multiple accounts located in different regions, buy PSN cards online and then buy whichever games you want from the foreign stores.
When does the store usually update?
Tuesday in North America and PAL countries, though some games are added throughout the week. Sales can go up at any time.
Do digital pre-orders offer pre-loads?
Often yes but the times vary depending on the game and the region. Usually it's a couple of days before release.
Are sales common?
The NA stores usually get a new sale every week and often get weekend-only flash sales. The PAL stores get a new sale every two weeks but often get new sales or additions in off weeks.
Sony's online subscription service. On PS4 you need it to play games online (excluding F2P and MMOs). On top of that, it offers cloud storage space on PS3, PS4 and PS Vita (1GB each on PS3/Vita and 10GB on PS4), exclusive betas/demos and the Instant Game Collection.
Instant Game Collection?
On the first Tuesday of every month, Sony updates the IGC with 6 new games, 2 for each system (though many are cross-buy). You can add these to your account and play them as much as you want, so long as you're subscribed to PS+. If your subscription expires, they are no longer playable but if you re-subscribe later on, they will be playable once more.
If you've got yourself a first or second generation PS3, your system is backwards compatible with PS1 and PS2 games. For every other PS3, they're only backwards compatible with PS1 games. The Vita is also backwards compatible with most digital PSP games. Sadly, so far, the PS4 isn't backwards compatible with anything. Hopefully that changes in the future but who knows. You can, however, use the PS3's remote play to play PS1 games on a PSP or PS Vita.
What can I play PSone Classics on?
Most of the PSOne Classics are compatible with PS3, PSP and PS Vita but it does vary with some games. The good news is all three support cross-buy, so any PS1 Classic you've bought for one system can be played on any of the other three systems, so long as they're compatible. You can also swap your saves between them. For a list of PS Vita compatible PSone Classics, check out the PS Vita thread.
What about PS2 Classics?
Currently, there's two types of PS2 Classics. PS2 Classics (PS3) and PS2 Classics (PS4). They're separate purchases and neither can use your old PS2 saves without jumping through a bunch of holes. But the difference between the two is the PS3 ones are straight emulated versions, while the PS4 ones are enhanced with trophy lists, improved resolutions and sometimes better performance.
Basically, 'buy one, get the other versions free' across PS3, PS4 and/or PS Vita. It works just as you would expect, you buy one version of the game and get the other versions for free. Just make sure you check beforehand because sometimes the PS3 version of a game may be the only version that's cross-buy (usually when the PS Vita version is cheaper) or the PS3 and PS Vita versions may be cross-buy but not the PS4 version (usually for a very late port).
It's what Sony has labelled cross-platform online play between the PS3, PS4 and PS Vita. PS3 players can play online with PS4 or PS Vita players and vice versa.
It means you can transfer your saves between different versions of a game.
OP shamelessly stolen from Unco-ordinated