DDO online has been a long running MMO in the industry, obviously following the wildly popular Dungeons and Dragons franchise. The game itself, which used to follow the monthly subscription business model is now entirely free to play, for the most part. If you want to just log on and play the game as you would every other MMO than nothing is different. However, like most free MMO's the game has now installed a micro-transaction store, as well as a possible subscription model.
The micro-transaction store is for very simple things, such as potions, armor, scrolls, and many other various items. Now Turbine themselves has explicitly stated that the most powerful items in the game still do not come from this store and are only from in-game quests. This is to help ensure that people with more money do not become inherently more powerful. The subscription system is a weird tie between the free to play game and its micro-transaction cousin. I would recommend reading the site for all of the gritty details.
For all of the information, please visit www.ddo.com.
