Every week sold must have a calendar week and unit assigned to it.
For simplicity, let's pretend there is one unit at that resort. There are 52 owners. Each owner owns one week, and that week number is on his deed. That serves the purpose of not overselling (e.g. the resort cannot sell 55 weeks or 67 weeks, when only 52 weeks are possible.)
In actuality, that timeshare system is "floating weeks". You do not have week 52 reserved for your use every year. If you did, that would be a "fixed week". In a floating system, you are competing with other owners to reserve the best week in your season. I do not know the Welk Seasons*. Most likely, high season is deemed to be summer weeks plus Christmas & New Years, for example weeks 24 - 36 and week 51 & 52 -- these are designated as the "highest demand weeks". Only the owners who own another high demand week can reserve those weeks, but you are competing with each of them to reserve your preferred week every year.
*Before buying, you need to understand how the Float Season to which your week belongs is defined. And how early are you allowed to reserve your preferred week. Do you log on to a website, or do you call? Then be sure to mark that day on your phone calendar, at exactly the time the reservation system opens and be ready to reserve your week. Don't be fooled - it is a competition, and you must be prepared in order to win.
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As of a couple of years ago, Welk switched its preferred exchange company to RCI. No, you do not get "points". You get a trading power unit (TPU) between 1 and 60. The highest is 60. You will trade a full week at Villas on the Green for a full week at another resort.
If you prefer Interval, some owners are still depositing their weeks at Interval, where they exchange for another week in Interval's system.