The whole picture
Green tea is the least processed of the true teas, once white tea is set aside.
The leaf is picked, fixed to stop oxidation, shaped and dried, and that is the whole craft.
Fixing, or kill-green（杀青）, is what makes it a green tea rather than something else.
Heat denatures the enzymes that would otherwise turn the leaf darker and softer.
In China that heat usually comes from a hot pan, which gives the nutty edge of Longjing.
In Japan it usually comes from steam, which keeps the colour brighter and the taste more marine.
Both are green tea, and the gap between them is wider than most categories manage.
Oxidation is stopped almost entirely, so the leaf keeps its green colour and its grassy bite.
China drinks more of it than of any other category, by a wide margin.
It also has the most regional styles: pan fired, steamed, roasted and sun dried all exist.
Famous Chinese names include Longjing（龙井）, Biluochun（碧螺春）, Huangshan Maofeng（黄山毛峰）and Taiping Houkui（太平猴魁）.
Japanese sencha, gyokuro and matcha come from the same plant and a different fixing method.
The cup runs from sweet corn and chestnut at the pan fired end to seaweed and spinach at the steamed end.
What unites them is freshness, and what kills them is age, heat and light.
How to approach it
Learn the process first, because every other distinction in the category follows from it.
Once you know what fixing does, the rest of the category organises itself.
Then learn four archetypes rather than forty names.
A pan fired Chinese green, a steamed Japanese green, a roasted green and a bud heavy green will do.
Everything else on a shelf is a regional variation on one of those four.
Drink them side by side, since the differences are obvious in the mouth and invisible on paper.
Two cups on the same afternoon teach more than a month of separate ones.
Buy in spring, when the new leaf arrives, and drink it within the year.
Green tea is the one category where freshness genuinely decides the cup.
Ignore grade names until you can taste the difference they claim to mark.
A first flush label means nothing if the leaf has sat in a warm warehouse since.
Ask for a harvest date before you ask for a grade.
That one habit separates good purchases from bad ones more reliably than anything else.
Buying and brewing
Brewing decides this cup more than it decides any other.
Water at 80 °C suits most Chinese greens, and 70 °C is right for a Japanese gyokuro.
Boiling water scorches the leaf and pulls out a bitterness no amount of quality will hide.
Use about 3 g of leaf for a 150 ml vessel, which is more than most people think.
Underdosing is the most common reason a green tea tastes like hot water.
Steep for roughly 60 seconds, then shorten each infusion after that.
Three or four steeps is a normal session, and the leaf tells you when it is finished.
A gaiwan gives the most control, but a small pot with a strainer works perfectly well.
A mug works too, although it holds heat in a way the leaf does not enjoy.
Buy 50 g at a time unless you drink it every day.
Store it sealed, cool and dark, and in the fridge if the bag is genuinely airtight.
Light and warmth are what turn a good green into hay within a few months.
Expect to pay more for an early spring picking, and check that is what you are being sold.
A cheap green drunk fresh beats an expensive one kept badly.
Where to go next
The most useful next step is a comparison rather than a purchase.
Put a pan fired Chinese green next to a steamed Japanese one and taste them together.
The contrast between nutty and marine is the whole category in two cups.
Then try a roasted green, which breaks the freshness rule on purpose and gets away with it.
After that, work through the regions: Zhejiang, Anhui, Jiangsu, Sichuan and Yunnan.
Each has a shape and a heat method that shows up in the cup.
Keep notes, because the differences are hard to recall a week later.
The dedicated brewing pages here go into temperature and dose in more detail.
The regional guides cover which famous names belong to which province.
If you want a category that keeps for years, look at white or dark tea instead.
Green tea rewards speed, and it punishes a cupboard full of unopened tins.
Drink what you buy within 6 months and the category starts to make sense.
Everything beyond that is detail you can pick up as you go.