The concept of a traffic exchange is simple - you surf for credits by visiting other people's websites. In exchange for credits other people will visit your website(s). 
 
Most traffic exchanges are free to join but many have upgrades that offer better terms of service.
 
They are great sites to advertise your affiliate programs' websites if you are on a tight budget.
 
Many successful Internet marketers use free traffic exchanges to build up profitable businesses. Their only investments are their TIME and COMMITMENT. To follow their paths of success, you need to be persistent and very passionate in your quest for success.