Sony is expanding how it offers games for the PS3 and PS Vita with the opening of the Sony Entertainment Network store. It acts very much like what the PSN Store is offering now, except this one is web-based and has other stuff for sale like music, TV shows and all that other stuff.
PSN users can log in using their PSN ID and can choose to pay for their purchases using credit/debit cards or from PayPal.
One important thing before you start purchasing stuff for your PS3 or PS Vita is that whatever you purchase doesn't automatically get downloaded on your device, but they are added to your download queue once you purchase the items.
To download the items you purchased off of SEN, it's the same as re-downloading items you purchased off the PSN Store. Here's a step-by-step guide for those not familiar with the process.
Sign into your SEN account, then select the Account Management option. Go to Transaction Management, then Download List, then select the content you want to download.
Curious PS3 and PS Vita users can check out what the web-based store has to offer by going to the "Games" section of the site. Bear in mind though, that not everything available on the PSN will be featured on the SEN store. However, if you're not near your PS3 and want to purchase something, this is still a viable alternative.
Thanks, Eurogamer