Unless using one of the above methods, cannabis is usually at least dried before use. Freshly harvested cannabis has too much moisture in it to be stable and will eventually mold unless a substantial portion of the moisture is removed.
On the other hand, dried but uncured cannabis is much more popular than having no cannabis at all, so it is frequently used in times of urgency, need, or occasionally greed.
Water curing allows for cannabis to be cured without being dried first (it can also be done with dried cannabis, but that adds an unnecessary step).
Speaking of mold, water cured cannabis should only be obtained from reliable sources, as it is sometimes used by unscrupulous folk to pass molded, insecticide-contaminated, or otherwise ruined cannabis onto the unsuspecting.
For smaller adjustments, the lid can be removed until a more acceptable moisture level is reached (a process known as burping).
The result of properly water cured cannabis is some of the smoothest smoke available, if that is how you chose to consume it. It is so smooth that many find the flavor (what little there is left) to be flat and boring.
Conventional, properly cured cannabis is dried as above and then placed into airtight containers and kept in a cool, unlit location to allow for the buds to mature and cure over a few weeks or months.
Drying is best done under mild conditions, as an environment too wet and cold can delay drying long enough to be a mold risk, and conditions too hot and dry can cause the outermost portions to over-dry while the interior flowers and stems are still too wet to be safely stored.
Some concentrate artists prefer to work with cannabis that has been immediately frozen after harvest. The material is rough trimmed while wet and then placed into containers and then into a freezer. This method eliminates the drying and curing steps, but is unsuitable for use for cannabis intended for smoking.
There are different methods of curing cannabis after it has been harvested, and which is best depends on personal preference.