The kettle is particularly useful for making tea but also for cooking, as it can quickly boil water and reduce waiting time during your cooking. It heats up and keeps the water warm, in any heat source it is placed. Tea leaves are not placed inside a kettle, only in the teapot where the tea is served. It is made of glass, a material with high thermal conductivity, which keeps liquids as warm as possible for a longer period of time.
The filter you have allows you to use tea leaves directly in the vessel, you can also control the steeping time of your tea to prevent excessive extraction of tannins.