Adaptive Content is a means by which the content shown to a user is adapted to best suit the user's requirements - perhaps based on their browsing device, their location or their browsing history. Here are some examples of the kind of things that can be achieved with an Adaptive Content Management System. Read more about Adaptive Websites.
1. Visitor Behaviour
Probably the most powerful example of an adaptive web page is the use of visitor behaviour to determine what content is shown. The online ad industry uses a crude version of this to display ads for products that you've recently viewed (when are they going to learn to not do that once you've actually already bought the product?). But if you can keep track of what your user is doing and you have the means to access that data in realtime, you have the means to construct pages which can be far more likeable for the user.
For example, a user that has visited 20 pages of your discussion site might be a good candidate for recommending they sign up, whereas a first time page viewer probably doesn't want to yet. Once they've signed up and made a few posts you might reasonably assume they have some emotional investment in your site - perhaps the time to prompt them to consider a paid subscription or at least a newsletter signup.
Someone who has browsed your broad-topic site extensively but has read only pages on a particular topic is easy to spot and easy to adapt to. Main menu items could be populated by related topics, whilst subtle leads to other topics could be placed at the end of a piece.
2. Time of Day
Knowing the time of day that the user is reading the site and applying some logic because of it is a powerful means of giving users content that they actually want.
Traditional media publishers have used this technique successfully for many years. TV programmes shown at breakfast time are distinct from those shown during the day, moving from morning news and magazine shows to addictive day-time programming. Kids' programmes are shown at "home from school" time. More magazine programmes are broadcast in the early evening, news in the mid-evening and entertainment later on. Same with radio.
An e-commerce site might show business-oriented products more prominently during the day, but consumer-oriented products at lunchtime and in the evening.
A news site typically shows breaking news where new stories replace older ones in prominence on the page. But the time of day might dictate the kinds of stories that are going to do well with readers.
Longer blog posts aimed at working 30-somethings are less likely to find favour during working hours, when shorted, snappier posts are would work better for reading instead of working. Come the evening the longer posts are more likely to be read. But on a blog for stay at home parents of school aged children, long posts might do better in the afternoon than in the evening.
3. Device and Connectivity
Adaptive allows you to go far beyond just changing the page layout and removing some blocks as you might do with a responsive design. A mobile user might want shorter articles, perhaps with a leaning towards more location and time specific information. A desktop computer user with a big screen might want greater levels of supplementary information displayed alongside the main content. And a laptop user might appreciate a lightweight version of a page if you determine that they're using a mobile phone to connect their laptop to the web.
One of the true beauties of the Write Once Read Anywhere promise of adaptive content delivery is the ability to provide syndicated content in different forms. Capturing appropriate meta data when the content is created means it can be used differently in different contexts. For example, if an article contains temporal or geographic information, attaching that information in a format that can be understood by the CMS means that it can make it available through syndication to appropriate recipients. So a travel blog with articles on different cities, if the locations mentioned in the article are captured in its meta data, could be syndicated within a mobile app providing travel information. A visitor to a new location could be offered a series of interesting articles on that place the moment they arrive.
5. Pricing and Product Selection
One of the most extreme examples of truly adaptive content is to change the prices for products or services on the basis of any of the factors that I've mentioned above (and more besides). I'm not advocating doing it, but it would certainly be possible to charge someone with a high quality mobile phone accessing your site on a fast connection more than someone on a dialup connection using a computer with a tiny screen!
That's a step to0 far in my view, but showing price-appropriate products to users would be a legitimate and useful approach that your users might appreciate.