FreeCell is different from most solitaire games in that you start with every card face up. There is one deck, and your goal is to build stacks in the foundation piles ascending from Ace to King of the same suit. When all foundation piles are complete, you win the game.
On the tableau you put cards in order from Kings down to Aces in alternating colors.
Though some rules vary, on the Solitaire Storm site, you can move a certain number of cards as a group. First, they must be a sequence of alternating color cards. Second, you can move a maximum of 5 cards at a time. This number is reduced for every free cell that is occupied. Put another way:
cards you are allowed to move at one time = 1 + number of unoccupied free cells
Ergo, if you have all 4 free cells open, you can move a sequence of 5 cards at a time. If you have no free cells, you can only move one card at a time. If you have 1 open free cell, you may move 2 cards at a time and so on.
As you may have guessed, FreeCell gets its name from the free cells in the game. So what are the free cells? They are holders for a single card. Any card may be placed there, but unlike the tableau piles, free cells may only have one card at a time. They are used strategically to open access to cards underneath it in the tableau. But given that using your free cells reduces your amount of cards that can be moved as a group, your use of the free cells must be carefully balanced.
On Solitaire Storm, you get unlimited undos so feel free to explore all of your options in pursuit of a win.