If you brew tea or coffee, you make it by pouring hot water over tea leaves or ground coffee.

A brew is a particular kind of tea or coffee. It can also be a particular pot of tea or coffee.

If a person or company brews beer, they make it.

A brew is a particular kind of beer or beer that is produced in a particular place at a particular time.

If a storm is brewing, large clouds are beginning to form and the sky is becoming dark because there is going to be a storm.

If an unpleasant or difficult situation is brewing, it is starting to develop.

A brew of several things is a mixture of those things.