I gotcha. A Keyword link is a link that the merchant has attached some good PPC bidding keywords to them.
So if you wanted to advertise a particular merchant's products in AdWords for example, you'd click the Keyword link and notice the merchant has suggested keywords you can bid on. This is also where they tell you which keywords you cannot bid on, non-compete keywords (keywords the merchant won't let you bid on), etc.
I know, it's not very clear and the only reason I know this is when I was an affiliate manager, my company used CJ to promote their affiliate program and I had the Account Manager explain it to me. Very strange way of setting that up if you ask me.