Gaps is probably my favorite Solitaire card game. It's fast, and easy to play and it's a lot of fun. The 2s are all placed on the far left, and the remaining cards are dealt into the 4 rows of 13. Then the Aces are removed to make gaps. You fill the gaps by moving a card into them that is one greater than and of the same suit as the card to the left, or one less than and of the same suit as the card to the right.
You're trying to arrange all the cards from 2 - King by suit. As you get cards into the positions that you need, they will get highlighted. When you run out of moves you can make, there is a shuffle button you can click up to 3 times. That will pick up all the cards that are not highlighted, shuffle them, and place them back into the rows. This will give you another shot at trying to get all the cards in a row.