Black tea generally should be made with water at a full, rolling boil, 212 degrees.
Oolong tea (also known as wulong tea) should be made with water a little bit below boiling, between 185 and 200 degrees. The water should be steaming rapidly and there should many bubbles rising in the kettle, but not really breaking the surface.
Green teas should be made with slightly cooler water, between 165 and 180 degrees. The steam should be wafting or gently swirling out of the kettle.
White teas should be steeped anywhere from 175 – 185 degrees, when you see the very first hint of steam.
Pu’er teas are very different. I have made them with cooler water, similar to a green tea but my favorite method is to make them with boiling water and steep them a long time.
Herbal teas should typically be made with boiling water.
Rooibos should typically be made with boiling water.