Not really as cpafromcroatia described.
Incentive offers CPA Offers - you're able to use them in content lockers, link lockers. They are mostly used to lock fake content so visitors rarely get anything like in free followers, game hacks niches...
Non incentive - these offers can't (shouldn't) be used for content/link locking. Advertisers want these offers to be completed only because the visitor is really interested in whatever they're offering.
In some cases, the visitor will get the reward, mostly if the reward is just something cheap, like beauty samples.
In other cases, when the reward is something expensive, like NFL Jerseys, they require users to complete the offer and later, buy some stuff from them in order to actually get reward. Anyway, you get paid even if they don't buy anything since they're paying you to get data for their potential customers, not for actual sales.