DNS propagation means the movement of new DNS data to different internet servers around the world. This process can take up to 48 hours before it is updated around the world. The importance of this DNS data is that it tells a users computer where to find your website, and therefore whilst it is still ‘propagating’ your computer may not know where your website.
This will affect you if you’re changing the name servers on your domain, updating A or CNAME records on your DNS zone, or modifying any other information contained in your DNS zone. This means planning your DNS changes at low traffic times, or if you are familiar with TTL’s (time to live), setting those to a lower value. Propagation starts from the moment you make any adjustment to your DNS configuration.