A pourer is an incredibly useful product, used (as the name suggests) to pour tea. It is usually a container (glass, ceramic or porcelain) into which the tea is poured after infusion and only then is it poured from this container with a spout or beak into individual cups for tea drinkers.
Why is the pourer used and not poured directly from the teapot? Because many teas are very delicate and delicate and demanding on the timing of the tea pouring. Just 3 more seconds spent gradually pouring the tea between each cup would affect (even negatively) its taste, aroma, energy… Therefore, the tea is quickly poured into 1 place = the pourer and only then poured into cups.
Also, the fact that the whole batch of tea is poured off at once causes the different strengths of the infusion to mix into one balanced one = when the tea is steeping, the strongest leach is down by the leaves, so that when the tea is gradually poured off, the first cups would have the weakest infusion in them and the remaining cups noticeably stronger.