What is it?

Possibly the ceremony was first exploited as a means of setting feudal disputes. It is held in cha-shitsu, a small Japanese room, usually surrounded by a carefully designed garden. It is usually a thatched-roof structure with plain plaster walls, whose several openings, placed at different heights and filled with shoji (sliding panels of wooded lattice covered with paper), admit a soft, diffused light.

Shoji

Cha-shitsu

The room is usually about nine feet square or smaller. When the guests are summoned they enter through a small nijiriguchi or "kneeling-in" entrance, about 2 1/2 feet square. The fact that guests must crawl into the room is intended to inculcate humility in all who enter or thought to have served the purpose of preventing them from concealing a sword under their robes.

The tea ceremony consists of the host first bringing the tea utensils into the room, offering the guests special sweets. The host prepares the tea, following a precise and intricate sequence of movement.
The host puts a little powdered tea in a bowl and pours on it water that has been heated over a charcoal brazier.
The tea is whipped to a froth with a bamboo whisk and then passed from hand to hand. The bowls are valued for their heat-retaining properties and the way in which they fit the hand as well as for their appearance.
The various utensils (the teabowl, tea caddy, water container, boxes, plates, and iron tea kettle) have been carefully selected by the tea master and are often of great age. The tea drinking is followed by a discussion and appreciation of the qualities of the utensils.