A goban is a board for playing Go (Wei Qi/Badouk). They come in many shapes and sizes, but what they all have in common is that they are divided into a square grid, with 19 lines in each direction. The 4-4 points, 10-4 points, and 10-10 point are marked with black dots for reference purposes. They are known as hoshi in Japanese or star points in English

Unlike in chess, stones are played on the intersections of the lines, rather than inside the squares. When describing moves, or keeping a record of a game, the points are usually labelled with numbers 1-19 in one direction, and letters A-T (skipping I, because a capital I is too easy to confuse with a lower-case L, or the number 1) in the other. Thus, a move on the hoshi (star point) in the bottom left would be called D4.

A traditional goban is like a small table. Made of an exceptionally thick and heavy (the one I picked up felt like about 20 kg) piece of wood standing on short stubby legs, they are usually about 50 cm x 50 cm and maybe 30 cm high (these are just my estimates... if there is an "official" size, let me know). The lines are carved into the top and painted (or scorched) black. Nowadays, most boards are much thinner and more portable, although they are still made of wood and bulkier than a standard chessboard.

Games other than Go can be played on a goban. Here in South Korea (where we call a goban a "badouk p'an"), popular games include a simple 5-in-a-line Tic-Tac-Toe-type game and a sillier game that involves putting five stones on the board and flicking them to try to knock the opponent's stones off the goban.

The goban has evolved somewhat over the years. As far as historians and archaeologists can tell, the original board size was 17x17 instead of 19x19. Smaller boards have also been discovered, but 17x17 seems to be the oldest. The size was presumably increased to 19x19 in order to increase the challenge, but no one is exactly sure when the change happened. It must have been a gradual change, because the oldest known goban is a 17x17 stone board found in Wangdu County in 1954, and dated as at least 1800 years old, but the oldest surviving game record, which is dated about the same as the stone board, is played on a 19x19 board (between prince Sun Ce and his general Lue Fan). Note that the Chinese claim that Go is much older than 1800 years (4000 years is a commonly quoted figure), so a different size of goban may predate the 17x17 ones, but this is the oldest evidence found to date.

This historical info was learned from http://gobase.org/history/

Many people have tried various sorts of alternative gobans. Playing on smaller (9x9, 13x13) boards is a popular way to teach Go to newbies. In Tibet, people still play on the older 17x17 format. 21x21 has been tried, but professional Go players say that gobans larger than 19x19 are too hard even for them. People have made gobans with the number of lines at each intersection greater or less than 4, gobans based on maps of cities or countries, and computers allow things like 3-D gobans, cylindrical (wrap-around) gobans, Moebius strip gobans, etc.