Newbie lurker question


I'm a newbie here and have been checking it out for a couple weeks. I have a question...I love expediton type rigs and remember reading years ago about the Camel Tropy in Autoweek. For all that time, occasionally I've seen pics of vehicles with cables (or so they appear) running from the roof racks to the front bumpers. What are these pieces for? Are they cables? What pupose do they serve? Thanks.