Ekiben is a meal box sold at JR stations nationwide in Japan.
Eki means station in Japanese and Ben is a abbreviation for Bento = meal box.
Japan has a rich gastronomical culture to carry bento and eat the meal outside.
Of course many Japanese make and bring their bento to their offices and schools but the difference between Japan and Europe is that bento are also sold in supermarkets, grocery stores, airports and etc.
Due to Japanese love to travel by train and eat by chopsticks(if you have to eat by silverware, you have to have a small table to put your ekiben. On the other hand, if you eat by chopsticks, you will use only one hand and the other can hold the ekiben which means no table needed) , ekiben is an ideal meal for them due to there is no dining car in Japan. Passengers have to buy their food before on board or some trains have staffs selling food and beverage on board pushing the cart. However the variation and number of ekiben are limited when sold on carts therefore most passengers by ekiben at the stations.
Then, not all ekiben are sold nationwide. As like the Japanese foods have local ones, types of ekiben is depended on the region. This ekiben shown on the photo is bought at Okayama station and includes scallops.
If you travel by train in Japan, do not buy sandwiches at convenience stores but buy the ekiben before getting on board.