The offer of places to eat in Tokyo is as varied as the city itself. Form luxury restaurants to cheap street stalls.
The local fast food consists mainly of ramen, sushi, tempura and beef rice shops. In these restaurants you can have a very decent meal for a few dollars. Do not worry if you do not understand the menu, most of the cheap restaurants have plastic food reproductions in their front windows.
For the mid range meals look for the food courts in the basement of the department stores.
In Tokyo you also find very upscale restaurants from all nationalities. Note that dining in one of Tokyo's finest restaurants can be extremly expensive.