Officially detailed around a year ago, PlayStation Now has been available in the US and Canada under an open beta scheme for all owners of PlayStation consoles and some Sony TVs (Samsung sets joining the fun too). And now it's finally arrived in the UK too as part of the country's own open public beta.

PlayStation Now is a major push by the gaming division of the Japanese firm and could well change the way we access and play games forever. But while the games industry has been talking about the prospect of cloud PlayStation gaming since the company bought Gakai and its games streaming technology in 2012, some outside of that bubble might not know what PlayStation Now is or what it will offer.

We hope to put that right here and, er, now.

PS Now is a cloud-based service much like Netflix or Spotify, but for gaming. It hosts a wide collection of PlayStation 3 archive titles initially (more than 350 games available in the States, over 150 in the UK), with the potential to include PSOne, PS2, PSP and PS Vita games too in the future. You can access them at your leisure, eventually playing them instantly on any device that has access to the service and a half-decent internet connection.

It uses technology acquired when Sony bought cloud gaming company Gakai, which allows you to play games that are not hosted on your own local consoles or other devices, but on massive servers elsewhere.

In a similar fashion to the now defunct OnLive or Nvidia's growing Grid service, the video of the game streams over the internet to the display you are using, with controller commands and your actions sent the other way. This happens instantly, so the effect is the same as if you are running a disc at home, but with no need for physical media or long downloads.

Streamed video is in 720p rather than 1080p. That won't matter on PSOne or PS2 titles, if and when they come along, but a dip in detail and picture sharpness will be noticeable for some of the PS3 line-up. Let's not forget though that a fair few PS3 games run in 720p anyway - including possibly the greatest game for the console, The Last of Us.

Interestingly though, there will be the ability to play multiplayer on certain titles and not just with other PlayStation Now users. Sony has said that in future you will be able to play against gamers using the disc version of the same game on their PlayStation 3 consoles.

PS Now games also reward gamers with Trophies like their disc-based counterparts, and you can still access messages about individual titles. Save games are stored in the cloud too, so you can pick up from where you left off no matter what device you played on last.

In the US, PS Now is available on PS4, PS3, PS Vita, the PlayStation TV set-top-box and select Sony Bravia TVs. Most of the US versions of the Bravia televisions released in the future will support the service too. As will Samsung Smart TVs released in 2015. They will also support the DualShock 3 controller - the same as used by PS3 - in order to play the games.

The UK launch is a little more limited, being restricted to PS4, PS3 and select Sony Bravia TVs and Blu-ray players.

READ: PlayStation 4 review

Eventually, Sony plans to expand access to PlayStation Now to other internet connected devices, mobile and tablets included. There is also a suggestion that this will include Apple products too, not just Android devices.

READ: Sony PlayStation TV review: For the gamers

It is recommended that you have a broadband connection of at least 5Mbps. Sony also suggests that you will get a more stable experience if you use a wired connection over a wireless one.

At present more than 150 games are available on the platform, with many more planned to be added over the coming months. Games available the platform include God of War: Ascension, the original inFamous and The Last of Us.

Currently, the US and Canada-based open beta offers games for one-off rental fees or, alternatively, on a Netflix-style monthly subscription model. You can rent single games for four hours from a fee of $1.99 (£1.18) for certain titles, $2.99 for more recent ones. The fees go up to $14.99 for 90 days rental of a single game.

The subscription model offers all-you-can-play access to a library of over 100 games. It costs $19.99 a month, or $44.99 if paid in three-monthly instalments. A free trial period is also available.

UK gamers can only rent games at present, which costs from £2.99 for 48 hours access to some titles, up to £7.99 for 30-days access.

READ: PlayStation Now finally gets a subscription option, $20 a month though

PS Now is now available for owners of the devices listed above in the US, Canada and UK as an open beta. It is not known when the full version will launch.

Owners of PlayStation 4 or PS3 consoles (with PS Vita and PlayStation TV access added for the States) can get to the PS Now games through the PlayStation Store. It is a dedicated section.

Sadly, after relaunching a couple of times, OnLive - PlayStation Now's biggest rival - folded, selling its technologies to Sony to help the company improve its service sometime in the future.

The only viable alternative therefore comes from Nvidia, with its lag-free Grid service. It is currently a free service for Shield Tablet and Shield owners and is capable of streaming games at 1080p in 60 frames per second. There are new games added all the time, but the current list already has a fair share of the biggest PC titles of the last couple of years.

A Shield Tablet can also be used with a HDMI cable and the wireless controller to play PC quality games on TV. A full version of the software will go live from 31 July when it will also adopt a subscription fee model.

READ: Nvidia Grid explained: Forget PlayStation Now, this could change gaming forever