A floating week is when you purchase a nonspecific week at your resort within a range of dates or season, say between the beginning of December and the end of February. So instead of owning that first week of December, you would own a week that you would need to use sometime during the entire winter season. The upside is that if you can’t make it on a certain date, you could now have the flexibility to choose a different date.
In a floating / flexible system, a fixed week is acquired, then deposited into a pool of other timeshares and consumers could choose the resort and accommodation, from the pooled inventory - if availability existed. Thus, the rights are floating / flexible and are classed as “floating rights”.
The downside is that accommodations are reserved on a first come, first served basis. And more often than not, the good times go quick. So you’ll have to plan far in advance to get the week you want, or risk losing out.