You need visitors to your website:

A major aspect in gaining Search Engine ranking involves getting visitors to your site - or traffic. Traffic Exchanges are excellent venues designed to create hits to your sites as well as getting them seen by the membership of the exchange.  There are two different types of traffic exchanges: autosurf and manual surf.  

Besides sending hits to your links via the surf, many exchanges also have banner and rotating text ad spots which are useful as well. 

What is the difference between Auto Surf and Manual surf?

Auto Surf sites rotate the links for you.  No clicking is involved.

Manual surf sites require that you click on an icon to exit the site being viewed and to bring the next site up in the surf bar.

Do You need both?

No, but it is recommended you have both types of exchanges in your marketing portfolio and that you actively surf those sites on a regular basis.  Auto surf is easy to accomplish and can generate many hits to your sites.  They are awesome traffic generators.

Manual surf is much more time consuming but you have a virtual ‘captive audience’ paying attention to your site while they surf.  For this aspect, they are perhaps more valuable to you when it comes to getting your site seen by human eyes.