Flower
The dried, cured bud of the plant, sold loose by weight in a jar or a sealed bag. It's the oldest format in the shop and still the one most people mean when they say cannabis. You can look at it, smell it, and choose with your own senses rather than a spec sheet.
It's taken by smoking — in a pipe, a bong, or rolled in paper — or by heating it in a dry-herb vaporizer, which produces vapour instead of smoke. Either way it arrives quickly and doesn't outstay its welcome, which is precisely why it's the easiest format to pace: you take a little, you find out where you are, and you decide from there.
How it's sold
By weight, in standard increments, in a childproof container with a label that names the producer, the batch and the lab that tested it. Larger amounts cost less per unit — which is the main reason people who know what they like buy bigger.
What to look and sniff for
Structure that isn't crushed to dust, visible trichomes (the frosty coating), and a smell that's loud and distinct rather than flat or hay-like. Dry, brittle bud that crumbles at a touch has usually been sitting a while. Ask to see the jar — a decent shop will always let you look.
Also on the flower shelf
"Smalls" or "popcorn" — the little buds from the same plant, usually cheaper for the same weight, and a genuinely good buy if you're grinding it anyway. Shake and trim are the loose bits, priced accordingly.