What happens when you update your DNS?

(jvns.ca)

I've seen a lot of people get confused about updating their site's DNS records to change the IP address. Why is it slow? Do you really have to wait 2 days for everything to update? Why do some people see the new IP and some people see the old IP? What's happening? So I wanted to write a quick exploration of what's happening behind the scenes when you update a DNS record.

Here's a great exploration of what’s happening behind the scenes when you update a DNS record.