To clarify, they are talking about custom fields for Clubs.
ACP > Community > Clubs > Custom Fields button
You can define custom fields for clubs to organize and sort.
With that said, I want to take a moment to provide comprehensive feedback to IPS in overall suite-wide organization and filtering. Most IPS apps use traditional top-down hierarchical organization like categories > subcategories. The hierarchy organization is the traditional, well-understood method of organization to all admins and is what is used most broadly in the suite. Both admins and users understand that you start at the top, then go through the categories -> subcategories to find your information. The live filtering, on the other hand, is becoming more widespread on the Internet and newer generations of users will be more comfortable with this dynamic view to immediately view the content without going through the levels of hierarchy. Regardless of how IPS wants to adopt each method, I think there's opportunity to apply it more consistently and with more depth throughout the suite.
This is how the IPS apps are organized:
Forums are organized by categories. Galleries are organized by categories. Downloads are organized by categories. Commerce is organized by categories. Pages / databases are organized by categories. (I'm sensing a pattern here ...)
Clubs are organized by live filtering. (Whoops, pattern broken).
It's no wonder that IPS clients have consistently and repeatedly requested categorization of clubs. It's been requested at least five times in the comments of the News announcement (here, here, here, here, and here). It's something that makes sense, is consistent with the rest of the suite, and is well-understood by users and admins. It's going to be very hard to break admins from their status quo of traditional organization.
With that said, I personally think the future is moving away from traditional organization to live dynamic filtering, so I'm glad you're embracing features like Fluid Forums and live filtering for Clubs. However, I think it's unusual that you offer the feature for only Clubs and not apply it to your existing apps. If you want clients to eventually embrace the live filtering as a concept, I think there's a huge opportunity to provide the fluid views to all of your apps.