The most important thing about Red/Black Tea is that it is fully oxidized. The tea leaves are rolled which causes the tea leaves to release polyphenol oxidase; when exposed to oxygen this causes the tea leaves to change from green to brown and eventually red. Heat is then applied to the oxidized leaves in the form of baking, frying, etc., in order to halt the oxidation process. As with all categories of tea, there are many ways to make Red/Black Tea and the specific processing methods often depend on the individual producer as well as region of production.
There is some confusion regarding the "correct" name for this category of tea. In China this category of tea is called Hong Cha (紅茶) which translates directly to Red Tea. The West calls this kind of tea Black Tea. Red Tea and Black Tea are names that refer to the exact same category of tea. From our point of view, the tea leaves generally look red and the tea itself looks red, so we prefer to call it Hong Cha/ Red Tea.