Similar to the concept I mentioned in Reciprocal Linking is Dead, you likely have come across this too. An indirect link is a link that doesn’t go to http://www.yoursite.com but instead passes though some other script firs, e.g. http://www.someothersite.com/out.php?yoursite
For the same reasons that reciprocal linking is considered worthless, indirect links are also; namely, they don’t improve your search engine rankings. And, for the same reason that reciprocal links still have value, so do these. Indirect links, from somewhere targeted towards your site’s niche or market, can still generate useful traffic.