There are two types of PTC sites: Bux PTC sites and Aurora sites.
The Bux PTC sites are more popular because they provide higher earnings.
The Aurora sites work in quite the same way as any regular PTC site. An Aurora site has both advantages and disadvantages to PTC site, but in the long term the advantages might outweigh the drawbacks.
The most important is that Aurora sites are more stable as they are more self sustainable than a Bux PTC site. They can rely on advertising income to sustain themselves. The Bux PTC sites are more likely to go bankrupt by a management failure due to the higher paying rate that is paid for a viewed adverisement, as the price of an adverisement pack sometimes does not cover the expenditure.
An Aurora site pays less for clicking the ads, but there are much more ads available to click (20-100 ads/day). By paying less for a click makes a great place for advertisers, as the advertisement packages are much more cheaper, they are affordable for every advertiser. Furthermore there is a so called Paid to Sign Up (PTSU) option at Aurora sites. That means you can take other members’ offers that are willing to pay you a certain amount ($0.05 – $1.00) if you sign up to a certain site, by the meaning of which you can earn more money than clicking the ads on a Bux PTC site.
As a general rule on an Aurora site you earn money after your referrals’ activity (clicking ads, signing up) even if you didn’t click any ads. That means if you have some referrals they make money for you even if you don’t log into your account for days. At a Bux PTC site clicking the ads is a must in order to be credited for the clicks made by the referrals.
Several types of memberships are available at an Aurora site for much lower prices than on a Bux PTC site. In addition, upgrading is combined with other features, such us advertising packages, credits, referrals. Buying or renting a referral is cheaper but the referral earning is lower, too.
The payout threshold is low, usually $1.00 or less.
To sum it up, a Bux PTC site is a faster earning + higher risk scheme while an Aurora is slower earning + more stable scheme.