Nasi means rice. We all know what box means. Put together, nasi box means "bento." It's basically Indonesia's version of a lunch in a box or sometimes dinner in a box.
This is the go-to type of meal for most of Indonesia's ministries and each ministry would have a favorite nasi box catering/restaurant it likes to order from. My directorate really prefers a Padang food nasi box called Wahid II, which is actually quite tasty.
There was a directorate once where I attended a meeting and the lunch box was hokka hokka bento, which is my least favorite of all the nasi boxes out there not only because I think "hokben" tastes like crap inside a foam tupperware, but it also banks on a gigantic portion of rice unbalanced by a tiny two-pieces of fried shrimp or chicken. Not really the healthiest of lunch or dinner meals.
I went to the Ministry of Defence once for a very long meeting, and that place gave all the attendees a huge box of D'Cost, a seafood chain.
Reliance on nasi box, though, can get a little overboard, in my opinion. Sometimes the catering people would just come and drop off the boxes, and we wouldn't know whose boxes they belong to so no one takes them. By the time we figure out that it's for us, the food inside is probably on the way to becoming rotten. And hence my stomach problems throughout 2011 when all I had every single day was nasi box (because I was at work 24/7... seemingly).
But getting nasi box certainly beats missing lunch because of a meeting, and nasi boxes saves me a lot of money. So there's the plus side.