The Wheel of Fortune Tarot card is the tenth card of the Major Arcana, which is the signifier of all of the tens of the Minor Arcana. Where the tens of the various suits represent changes to that particular aspect of life that they represent, the Wheel of Fortune represents major life cycles and changes to just about every aspect of one's life from that point forward. You can understand how far-reaching an effect this card has if you consider the effort it takes to pack up a home and move from one place to another or to make a sweeping change in careers from one to another.
This is what the Wheel of Fortune represents -- those types of major considerations one must face to move onto the next step along a path, if not a new path altogether.
Being a Major Arcana card, it would be foolhardy to try to explain all of the aspects it represents, so I will consider the larger ones. Being a major life-cycle and change card, it represents on a surface level the transition from concern for oneself to consideration of others' concerns, as well as the way one first interacts with life in general. It denotes that one has established a solid foundation for oneself.