1. A standard tea cup is usually 6 fluid oz (USA). A standard cup in the USA is 8 fluid oz. This is important because many times, you'll come across measurement information for a recipe on the web that may be the five hundredth iteration of a recipe. And sometimes, what was originally measuring ingredients per cup of tea becomes ingredients per cup. Just something to be aware of.
2. Steeping the tea (letting dry tea leaves sit in hot water) is also called brewing tea. A tea kettle is for boiling water. A tea pot is for brewing tea.
3. In the UK, tea made from tea leaves is called tea. Tea made from herbs or flowers to drink as a beverage is called an herbal infusion. Tea made from herbs or flowers for medicinal reasons is called a tisane.
4. In the USA, tea made from tea leaves is called tea. Tea made from herbs or flowers is also called tea, or herbal tea if we're being specific. There is no distinction between beverage and medicinal teas. My Irish mother thinks using the term 'tea' for herbal infusions and tisanes is insanity.
5. Making herbal tea is not the same as making tea from tea leaves in one important way: steeping time. Tea leaves are steeped for shorter times than herbal teas, even as short as a minute for some green teas. And of greater importance, if they are steeped for too long, over 7 minutes at the most, they will actually acquire a more bitter flavor.
Herbal teas, on the other hand, are usually steeped for 5-15 minutes, but they do not grow bitter, only stronger, and can be steeped for significantly longer times if desired. For herbal tea that you are making for medicinal reasons, this could affect the strength of the medicinal components, so be careful in that regard.
In my experience, there are some herbs that take on a different flavor if they are steeped too long. For example, with rosemary or pineapple sage, longer steeping times added a bit of an unpleasant, piney flavor to the tea. There are also herbs that were much better after a very long steep, like stevia, which is much sweeter after a 24 hour steep.
7. General rule of thumb: 1 teaspoon of dried tea material (leaves, flower petals, crushed seeds) per tea cup (6 oz). Although some tea is very light and fluffy, and some is very dense, so that changes things a bit. Previously, in this post on tea, I had down 1 tsp of dried leaves per cup, which would be 8 oz. I suspect the 6 oz information is closer to correct, based on the sources involved.
8. Tea made from dried ingredients is actually better than tea made from fresh plant material, typically. This is because the dried leaves release their contents better into water than fresh plant leaves and flowers do. You'll get more flavor, and more medicinal components, I understand, from plants that has been dried properly, which in my opinion is drying without heat, if possible.
A local herbalist in my area
My mother, from a nation of tea drinkers
a great site on tea facts and brewing tea: http://www.theteatable.com/tea101_teafaq.html