Ekiben is a word from eki “Station” and bento “lunch box”. They are only offered at certain train station.
If you are taking the train with assign seat, you should always try an Ekiben instead of eating junk from the combini. Stations like Shinjuku, Tokyo or any other station where the Shinkansen goes trough have a shop that sells only ekiben. They are a bit more expensive than your regular bento from Lawson, but well worth it. The ekiben on this picture is salmon and ikura(roe). Some people call this a “Salmon oyakodon”12