Your free web address
Every site gets an address of its own at no cost, set up for you the first time you publish. You never have to buy anything to be online.
Your site does not need you to buy a name before it can exist. It gets a free web address of its own, and that address is a real link you can send to anyone.
Before you publish
While you are building, your site is live in front of you — the real thing, not a mock-up — but privately. Only you and the people you have invited can open it.
That is deliberate: you should be able to spend a week getting it right without a half-finished page sitting where a customer might find it.
When you publish
The first time you publish, your free address is set up for you automatically. Nothing to choose, nothing to configure, nothing to pay.
You will find it in your project's settings, under Domains, listed first as the site's main address. That is the link to put in your social profiles, send to customers, and print on a card if you are in a hurry.
Visitors reach it over a secure connection — the padlock is set up for you and you never see a certificate.
It is a real address
It works everywhere a web address works: shared in a message, opened on a phone, found by a search engine, linked from your social pages.
The only thing it does not do is carry your name — it is an address Spanli gives you rather than one you own. For most people that is perfectly fine for the first weeks or months, and some sites never need anything else.
When you get your own name
Buying or connecting your own domain does not take the free address away. Both keep working, so links you already gave people keep landing on your site.
See Using your own name.
Changing it
The free address is derived from your project's name and is not something you can rename afterwards. If you need a different address, that is what your own domain is for — and it is the better answer anyway, because that one is yours.