FQDN

A fully qualified domain name (FQDN), sometimes also referred to as an absolute domain name, is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including the top-level domain and the root zone. A fully qualified domain name is distinguished by its lack of ambiguity: it can be interpreted only in one way. It usually consists of a host name and at least one higher-level domain (label) separated by the symbol "." and always ends in the top-level domain.

The hierarchy of labels in a fully qualified domain name (Above)

Domain Name

A domain name is an identification string that defines a realm of administrative autonomy, authority or control within the Internet. Domain names are used in various networking contexts and for application-specific naming and addressing purposes. 

Use in web site hosting

The domain name is a component of a uniform resource locator (URL) used to access websites, for example:

• URL: http://www.example.net/index.html
• Top-level domain: net
• Second-level domain: example
• Hostname: www

IP Address

An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. An IP address serves two main functions: host or network interface identification and addressing.

Video: DNS Explained

Video: IP Addresses

Discussion

Read this article. https://en.wikipedia.org/wiki/IPv4_address_exhaustion

What are your thoughts on the future of IP addresses? Can you think of an alternative solution to the one that has been proposed? https://tech.slashdot.org/story/14/02/17/1319204/whatever-happened-to-the-ipv4-address-crisis

Additional Reading and Resources

https://en.wikipedia.org/wiki/Domain_Name_System

https://en.wikipedia.org/wiki/MX_record