A solid shaving soap is placed in the top of the mug (the first bar comes with the kit, and you can always buy a replacement bar later), and warm water is poured through the spout to keep the lather from getting cold.
A mug with a comfortable handle and a large spout to place a shaving brush on.
The bowl has holes to allow any residual moisture from the soap to drain out. This makes it easier for the soap to dry.
Such a bowl will be appropriate for home use by vetshaving connoisseurs and for barbershop.