Millions of japanese of all ages carry their o-bentoh (お弁当) along every day. You propably got it, I’m talking about the “honorable lunch”!
But the main difference between the bentoh and our western lunchboxes,
is that the basic ingredient is not bread, but rice (indeed, most japanese people eat rice (at least) twice a day -even three times, when they get it for breakfast). Other foods, called o-kazu (おかず) are served with rice. In English, one would say: the main dish, but japanese cuisine rather consists out of a great variety of small dishes. This is true for the bentoh.
There are many kinds of bentoh: industrially produced (packed in a plastic tray, and sold in combinis), prepared every morning by the mother for her children (packed into a nice little handkerchief), or the ai-sai-bentoh (愛妻弁当, prepared by the youg wife by love for her husband), without mentioning the eki-ben (駅弁, sold in train stations and which gives you a foretaste of travel)…