I have 30 websites and just looking at changing my hosting provider but I have bit confused, some say unlimited domain names, but they are sub domains. Some say for instance 10 dedicated IP addresses. Im not actually quite sure what the difference is?

Subdomain is generally known as a “Domain within a Domain”, subdomains are web addresses built upon an existing domain name.
And dedicated IPs are quite different independent IP addresses.

Unlimited or multiple domains should mean the number of domains and not subdomains, as the number of subdomains is usually unlimited with every host.

Dedicated ips are more benefical than sub domain