DNS Stands for Domain Name System. At its core, DNS Resolution is the Yellow Pages (Phone Book) for your Domain Name. Your DNS will contain records that specify information pointing to different services such as your website and email hosting.
When someone browses to a website, for example www.customerdomain.co.uk, your web browser will then do a DNS lookup in order to see where it needs to point to in order to view the information that you have requested. This is done by looking at where specific DNS records for your domain name are pointing to.
You can learn more about specific DNS Records and what they do by Clicking Here.
You can learn more about specific DNS Records and what they do by Clicking Here.