This is a typical warung: a roofed metal frame with sheets hung on the outside. The fabric serves the double purpose of advertising the menu and giving diners a modicum of privacy.
This place lists "Internet" at the top of its menu, along with roasted bananas, boiled noodles, fried noodles, and soft-boiled eggs. I initially wrote that there must be a computer place behind the warung, but in fact, as Treespotter astutely points out in the comment section, this is actually an abbreviation for noodles with an egg and corned beef (Indomie, Telur, Kornet). They also offer an assortment of juices, from avocado to guava, and other drinks including milk with raw egg, honey and ginger (Susu Telur Madu Jahe, abbreviated STMJ).
Last but not least, there's kopi susu, probably made with half as much coffee and twice as much condensed milk as I use at home.
Warungs are where most people eat most of the time, since they're fast and cheap. You can also get food from the carts that make the rounds of all the streets, but there's only a few kinds of carts: they'll usually offer fried rice or meatballs-and-noodles or chicken-and-noodles. In Jakarta they'll also have ketoprak, which is tofu and bean sprouts with peanut sauce, especially in the morning. But if you want more variety you go to a warung.