This doesnt appear to be a technical term for me at least. What I gather from your description is hosting DNS services with an external entity.
For example, if I have a company and I need to host say a web site, I'll need DNS services to map the host names (www.domain.tld & domain.tld) to the website's IP address. I could either host my own DNS server(s) within my production network, or host them externally, with a DNS provider.
is it possible to have email server in one service provider and have website hosted into another company.?
Yes, absolutely. You manage that via your DNS records. For example. lets say you have a website with provider-1 and email services with provider-2. your records would be set up something like this...
(A) domain.tld --> ip address of provider-1 where website is hosted
(CNAME) www.domain.tld --> points to your domain.tld (like a shortcut)
(MX) domain.tld --> points to smtp1.yourEmailProvider.tld (example)
(MX) domain.tld --> points to smtp2.yourEmailProvider.tld (secondary smtp server)
(A) server1.domain.tld --> points to a server in your network (example that points to neither your website provider or email provider)