kashrut

Question

I'm sorry of I'm asking a question that's been answered before, but I just came across this website, and I see that there are foods listed as kosher which do not have a hechsher on them. While I don't doubt that the ingredients are kosher when listed how do you know how the food or gum is made? how do you know that these foods aren't made with the same utensils used for non-kosher products? how can it be kosher without a mashgiach? thank you