Sequences of cards in the tableau may be moved as a unit, but only if there is room enough on the freecells and tableau columns and tableau gaps to move them one at a time. This is just a convenience for you to make it easier to play the game. To determine how many cards you can move in sequence follow this formula. Multiply the number of open freecells by the number of gaps in the tableau (BUT do not include a gap in the tableau if you are moving a sequence to that gap!), then add the number of gaps in the tableau, then add one more. You can do this because gaps can hold more than one card while freecells can hold only one card.
So, if you have two open freecells and two gaps in the tableau, and you are not moving your sequence of card onto one of the gaps, you can move a sequence of 7 cards:
(2 * 2) + 2 + 1
It is best to keep as many freecells empty as possible. This allows you to move more cards in sequence, and allows flexibility in moving cards around the tableau. If at all possible, try to move cards onto the freecells only when necessary, and only when you can move them back off the freecells back onto the tableau piles, or foundation, as soon as possible.
Cards may not be moved from the foundation back to the tableau or onto any of the freecells. Because of this, it may make more sense to keep cards on the tableau and in the freecells, and available for play, rather than moving them early on to the foundation.
Creating a gap is usually a good move in Freecell Solitaire. When you have created a gap, try to fill the gap with as large a sequence of cards as possible.