Board - broad
Confusing board and broad is an easy typing error to make. Don't make it!
A board, as a noun, is literally a piece of wood. It is a long, thin, broad plank. This leads to many special types of board which are no longer necesssarily made of wood: 'cardboard', 'notice boards', 'circuit boards' in computers, boards as a name for the covers of hardback books, 'ironing boards' and 'chess boards'. Figuratively, the noun board has several other meanings. It may be helpful to some students to know that it has been used metonymically to mean 'the stage', or theatre as a profession: "he treads the boards" means "he is a professional actor". More historically, a board often meant a dinner table: a "groaning board" was the mark of a generous host. The meaning of 'table' is also to be seen when various committees, which sit round a table, are called Boards: university students have probably heard of 'Academic Boards'.
As a verb, 'to board' means to go onto a ship, or other means of transport; it can also mean to stay in someone else's house as a lodger, eating with the owner. (The phrase for having all meals is full board; one or two meals is half board. If you have no meals with the owner of a house where you are staying for payment, it is called lodging; meals with accommodation generally is called board and lodging.) The verb gives several other words and phrases, like on board to mean 'on the ship, or train, or aeroplane; the adverb aboard ("All aboard!" is an anouncement that everyone who wnats to travel should now be on the vehicle.)
The adjective broad is basically the opposite of 'narrow'. It is close in meaning to 'wide'. (The differences in idiomatic use of 'broad' and 'wide' can be difficult for non-native users of English. Ask a native speaker for advice with which word to choose in the context that you are working in.)
For the many detailed meanings of both these words, see a good dictionary.