There are two major types of timeshare "weeks" ownership:
Deeded - meaning that you own a part of the timeshare resort.
Right to Use ("RTU") - meaning that you have the right to use the timeshare for a specified number of years under a long-term lease.
An RTU timeshare might have residual rights, meaning that there may be some value in which you will share if the property is sold at the end of the lease. Those residual rights, if any, are detailed in the legal documents for the resort.
If an RTU timeshare has a remaining lease of (e.g.) 25 years or more, you shouldn't care much about what those residual rights are. Buy to enjoy 25+ years of vacation and, if you're really lucky, you'll get a few bucks (in terms of today's value) when the lease is up.
However, if the timeshare has a remaining life of only a few years, those residual rights would be very important in determining your offering price for a purchase.