What it actually does
A ceramic coating bonds to the clear coat and leaves a hard, water-repellent surface. Dust and water sheet off instead of baking on, so washing takes far less time and far less scrubbing — and less scrubbing is what really keeps paint looking new.
It also holds gloss through a summer that normally dulls it, and gives some protection against the light etching you get from bird droppings and sprinkler water if you rinse them off reasonably soon.
What it does not do
It is not armour. It resists the fine swirl marks that come from washing, but it will not stop a stone chip or a car park scrape. Anyone promising that is overselling.
It also does not remove existing damage. Whatever is in the paint on the day of application gets sealed under the coating — which is exactly why the preparation matters more than the bottle.
Preparation is most of the job
A proper job is wash, decontamination, then machine correction to level the swirls, and only then the coating — cured indoors, not rushed in the sun.
That prep is the bulk of the labour and the bulk of the price. A cheap coating quote almost always means the prep was skipped, and a coating over swirled paint just locks the swirls in.
Making it last
Wash with plain water and a pH-neutral shampoo, two buckets, and dry with a clean microfibre. Avoid the aggressive brushes at automatic washes — they undo in one pass what the coating is there to prevent.
Bring it back for a maintenance check around the year mark. That is when a top-up costs very little and keeps the surface behaving as it did on day one.