Infuser
A tea infuser is a device in which loose, dried tea leaves are placed for steeping or brewing, in a mug or a teapot full of hot water; it is often called a teaball or tea maker, and sometimes a tea egg. The tea infuser gained popularity in the first half of the 19th century. Tea infusers enable one to easily steep tea from fannings and broken leaf teas.
Some infusers are removed along with the tea leaves from the pot, while so called shut-off infusers are left in the pot after the brewing process is complete.
Use
A tea infuser performs a similar function as a tea bag, a later American invention. The infuser is generally a small mesh or perforated metal container or covered spoon that holds tea leaves, in varying sizes to steep single or multiple servings at once. Common shapes for infusers include spherical, conical and cylindrical. One style of infuser is a split sphere with tong-like handles to open its mesh container.