It means pointing your domain to one of several websites, so that when visitors go to your domain they have the option of clicking on paid-per-click (PPC) ads. As domain owner, you get a portion of the PPC revenue.
Popular ones right now are domainsponsor.com, fabulous.com, domainhop.com, sedo.com, and afternic.com. Each has their strengths and weaknesses, and I'm sure others can recommend more outfits than the ones I listed.
DNS changes are not instant. While some TLDs update really fast, it could take 48 to 72 hours to fully-propagate throughout the entire internet, and some really sucky ISPs cache DNS lookups longer than they are supposed to. So if you "just removed" the redirection, you may have to wait a few days to see the change.