How do these companies give you traffic to your website?

I see these companies saying they will give you traffic to your website. How do they do that?
Answer #1
Not worth it =/
Answer #2
U pay=They make bots visit ur site=$$$ for company.
Answer #3
vishnubabu replied: U pay=They make bots visit ur site=$$$ for company.
very true, they setup referral links through their domain (or another domain they own) and have the bots visit them.