Does ABP for IE block ads, or hide them?

[jusob]

It looks like Ad Block Plus for IE hides ads by running Javascript on the page rather than blocking the HTTP/HTTPS request for the ad. Am I wrong? I couldn't see any explanation of how ABP for I works.

[Thunder Dan]

With some (if not all) ads it appears to be only hiding them because sometimes an ad will briefly appear and then disappear when a page is loading. However ads that play before a video on sites like YouTube seem to be truly blocked.