Freecell is a classic solitaire card game where you have all the cards in the deck dealt out into 8 columns. You can build the columns down alternating colors. In the top right of the game screen you have four suit piles that you are trying to build up from Ace to King by suit. On the top left you have four Freecells. Each Freecell can hold a single cards from the columns. You can use this to move cards out of the way temporarily as you move the cards about in the columns.
One feature in this version of Freecell that is not a standard rule is the ability to move fully packed series of cards. I added this feature by the request of several users, and I feel like it speeds up game play. If you're not a fan of this feature, I also have Classic Freecell with the traditional rules.