You can buy short or long tern access to certain games (full access means you pay once and can play it as long as it is supported, which they say will be as long as people are still playing, but at least 3 years after release), or there is a subscription pack that will let you play any of the bundled games and give a discount on others. Most games also have a demo, which are apparently the full games, since they say you can continue with the same save if you try a demo and then purchase access.
Getting Started FAQ
