Kanda is an area of Tokyo, located to the northeast of the Imperial Palace, more or less due north of Tokyo Station.
Nowadays, it's hard to define Kanda precisely. Before World War II, Kanda was a ward of Tokyo City; in 1947, it was merged with Kojimachi Ward to form the special ward now known as Chiyoda. Most parts of the old Kanda Ward still have "Kanda" in their addresses somewhere.
Part of the confusion about the identity of Kanda stems from the fact that there is a "Kanda" station on the Yamanote Line, but the station is almost on the edge of what was historically known as Kanda: Akihabara, Ochanomizu and Suidobashi are also in Kanda. The tendency nowadays is for people to conceptualize areas based on the closest station, so "Kanda" is now often interpreted to mean about a quarter of what "Kanda" has historically denoted.
Being in a central area of Tokyo, Kanda has a lot going on. Four of Japan's largest universities--Nihon, Chuo, Meiji and Senshu--are located in Kanda, and this academic concentration led to the emergence of Jimbocho, a district that is probably the closest brick and mortar equivalent to Amazon.com in that you can find any kind of book there. Also in the old ward: the world-famous Akihabara electronics district, officially called Soto-Kanda or "Outer Kanda."
The name literally means "rice paddy of the gods." The name comes from a large Shinto shrine in the area, Kanda Myojin, which dates to 730 AD (at which time it was actually surrounded by rice paddies). When Japan was being parceled out into neat little municipalities in the late 1800s, the name of the shrine was chosen to represent the whole area.
Nowadays Kanda is largely commercial property, and the area houses offices for many small and medium companies (larger firms tend to prefer Otemachi and Ginza, just to the south, or the Kudan area to the west). There is a sizable residential population, but the area is not particularly fashionable and so luxury housing has failed to emerge there, despite the convenience of the area to many key districts of Tokyo.