What is PTC?

Paid To Click is an online business model that draws online traffic from people aiming to earn from home. Paid-To-Click, or simply PTC websites act as middlemen between advertisers and consumers; the advertiser pays for displaying ads on the PTC website, and a part of this payment goes to the viewer when he views the advertisement.
The viability of the PTC business model has been questioned, as fraudulent clicks have ramped up the expenses for advertisers.[1] With lawsuits filed against the internet search companies, the burden has been placed on Google, Yahoo and others to determine the valid clicks from the fraudulent ones,[2] although PTC site may just be used as advertising, to direct traffic to one's site. Moreover, many users registered in PTC websites are bots.
Even though advertisement is the most widely known method for PTC to stay alive, most of the profit comes from the direct sales of fake referrals which are created virtually by the PTC owner at his will. To cover up all this scheme, PTC owners inject some normal ads from fictional advertisers, thereby keeping the system running smoothly.
Some PTCs are also used to mimic mass human traffic, which can help a botnet stay undercover and perform click fraud activity in second and third-tier ad networks. Many PTC owners also pollute the ads with malware and botnet rootkits.
Scams, although exposed on various PTC forums, are still heavily used by newcomers who are drawn in to the websites by search engines. Scam PTC sites are known to attract new users with cheap offers for upgrades and referrals and disappear without trace after a short time.

Reference

http://en.wikipedia.org/wiki/Paid_To_Click