DNS, or Domain Name Service, is what takes human-readable names, such as www.google.com and turns it into an IP address, such as 18.104.22.168 (Both will take you to the same place).
If we didn't have DNS, we'd have to memorize the IP addresses of all the websites we visit, and 'virtual' websites that exist on a single server (some servers hold hundreds of websites) would not be accessible because they need the correct header in the HTML request, which if you go to the server by IP address, you won't get.
The last few days several of my clients and people I know have reported DNS irregularities. It looks like some of the Top Level Domain (TLD) entries for whom is reported as the Source Of Authority (SOA) for different domains are reporting incorrectly.
What does that mean in simple terms? It means that when you go ask the big 13 servers that run the internet who you need to talk to in order to find the IP address that goes with the website you are trying to go to, like www.google.com, is giving you the wrong server to ask. In that case, you never get the correct IP address for the domain, or you get none at all.
Very weird. More details to follow.