The subscription option is plain and simple. If you choose, you may purchase a subscription. There is nothing – absolutely NOTHING – in the game that you have to pay for to unlock. You get 100% of the content without ever having to pay a single, thin dime.
The game is 100% free to download and install and you get 100% of the content without ever having to pay a dime. This is great because it certainly allows people to get in and experience the games at no cost. One of the new and exciting things about SOE's business model is their new free-to-play concept, which makes all of their games free of subscription fees.
You want a comparison? There! Now GET! Free to play?