How do they do this?

I have some html code that is a list of newsletters that was given to me by an affiliate. When submitted, this goes to a php page. Can someone tell me how this page gets all of the values that are checked? I thought that it was handling it all in an array, but I have been unable to verify this. Can anyone help me understand it? Here is the code from the page that has form. <BR><INPUT type=checkbox name=listname value="fabfree/Recipes.list">Recipes <BR><INPUT type=checkbox name=listname value="fabfree/HUMOR.list">Humor <BR><INPUT type=checkbox name=listname value="fabfree/beauty.list">Beauty <BR><INPUT type=checkbox name=listname value="fabfree/gambling_and_lotteries.list">Lotteries <BR><INPUT type=checkbox name=listname value="fabfree/Contests.list">Contests <BR><INPUT type=checkbox name=listname value="fabfree/Gambling.list">Gambling <BR><INPUT type=checkbox name=listname value="fabfree/Computer_Software-Educational.list">Software-Educational <BR><INPUT type=checkbox name=listname value="fabfree/COSMETICS.list">Cosmetics <BR><INPUT type=checkbox name=listname value="fabfree/WEIGHT_LOSS.list">Weight Loss <BR><INPUT type=checkbox name=listname value="fabfree/Genealogy.list">Genealogy <BR><INPUT type=checkbox name=listname value="fabfree/Health_and_Fitness.list">Health And Fitness <BR><INPUT type=checkbox name=listname value="fabfree/JEWELRY.list">Jewelry <BR><INPUT type=checkbox name=listname value="fabfree/Clothing-Catalogs.list">Clothing-Catalogs <BR><INPUT type=checkbox name=listname value="fabfree/EDUCATIONAL_TOYS_AND_GAMES.list">Educational Toys & Games <BR><INPUT type=checkbox name=listname value="fabfree/TOYS.list">Toys <BR><INPUT type=checkbox name=listname value="fabfree/HOBBIES_AND_GAMES.list">Hobbies And Games <BR><INPUT type=checkbox name=listname value="fabfree/Astrology.list">Astrology <BR><INPUT type=checkbox name=listname value="fabfree/CRAFTS.list">Crafts Thanks CDitty