It started as a simple idea based on the assumption that people don't need vacation lodging except for a week or two a year. Take a house, cabin, condominium, or villa, and divide ownership into 52 weeks (in practice it's usually divided into 51 weeks with one week allowed for maintenance). It allows you to purchase the time spent as vacation lodging, and 1/51 of the ownership of the home. The next logical step in the development of timeshare was to be able to exchange time in these places between people who want to vacation in different areas each year. So, the two entities you'll likely be dealing with are the resort lodging, or timeshare itself, and an exchange company.
The number of systems in use for buying timeshares has grown tremendously in recent years, but three systems are commonly in use: fee simple, leasehold, and right-to-use (RTU). With fee simple you buy a portion of the property outright and own title to that portion. Under the leasehold system you own the property, but only for a specific length of time. With a right-to-use system, you don't actually own the property, but are purchasing a right to use the property for a certain amount of time and for certain weeks of the year. There are many reasons why you might want to sell your time share. One reason may be that the time share no longer fits into your lifestyle. Perhaps you now have a family with young children and no longer want a time share in an adult resort area. Or perhaps you have reached your retirement years and are looking for a time share that has more to offer you such as golfing or the ability to travel at any time of the year. Another reason that you might want to sell your time share is because you can no longer afford to pay the taxes, maintenance fees, or mortgage on your time share.