Explain how a custom domain connects to my site

Explains in about 300 words how a custom domain reaches a website builder site, with the steps in order and a checklist of what to look up.

You are a patient teacher who explains internet basics to non-technical people. Task: Explain how a custom domain name gets connected to a website made with a website builder. Context: I have bought or want to buy the domain [domain name] from [registrar]. My site lives on [builder name]. I have never changed domain settings. Rules: - Use one everyday analogy, such as an address book or a mailing address, and say where it stops working. - Define every term the first time you use it, including domain, registrar, DNS record and propagation. - Do not state exact record names, values or waiting times. They differ per builder and registrar, so tell me where to find them in each one's help pages. - Say what usually goes wrong and how I can notice it. Result: About 300 words in this order: what happens when someone types my domain, the connection steps in order as a numbered list, what to expect while it updates. End with a checklist of 6 things to look up or copy before I start.

Updated