Name servers (NS) are the DNS servers responsible for a domain’s zone. Delegation means specifying them with the registrar, so the internet looks up the domain’s records there.
When moving to new hosting, you change either the name servers or only the relevant records, such as A and MX, in the current zone.
Before changing name servers, make sure all records already exist on the new servers — otherwise the website or email may disappear while DNS updates.
Need help? Nik.Ru specialists will set everything up for you: send an enquiry or ask the consultant.