Certain teas are best when brewed in a kettle, that boiling the water with the leaves inside. This is the difference we make between the word “steeping” and “brewing”. We use “steep” to mean infusing the water (hot or cold) with flavor extracted from the tea leaves, but without heat being applied. In contrast, brewing means boiling the water with the leaves inside as heat is applied.
This is often best with roasted tea leaves such as hojicha, kyobancha, etc. or with herbals such as mugicha.