Sometimes parameter values completely change the content of the page; sometimes they only reflect a re-ordering; sometimes they do not change the content at all but reflect a referral or tracking campaign or some other information. By default Bing understands each unique URL as a unique page, which can lead to "duplicate content" being indexed and potentially penalized or at least different backlinks with split link juice even though they may point to the same page and content.
So by default the parameters are "Disabled," which means Bing will treat any URLs with unique values for those parameters as unique URLs. i.e. if Parameter "rows" was disabled:
http://www.example.com/?rows=10
http://www.example.com/?rows=20
If you change the status to "Enabled," Bing will ignore that parameter on any URL in your site, implying that it represents a slight change or no change at all in the content of the page and allowing you to not split your link juice among them.
http://www.example.com
See this SEOmoz post, scroll down to IV (9).
In the same section of BWC ("Index"), there's an option called "URL Normalization". The name implies Bing treats this more like canonicalization, but there's only one option – "ignore". Like Google, you get a list of auto-detected parameters and can add or modify them.
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As with the GWT tools, I'd consider the Bing versions to be a last resort. Generally, I’d only use these tools if other methods have failed, and one search engine is just giving you grief.
The wording by Bing is a little confusing, but I think the idea is that you "enable" or "disable" the ability to ignore the parameter.
