The IANA registries fall into three broad categories, with every category relating to a specific function of the Internet. The first is IP addresses. Here, it includes the global registry for IPV4 and IPv6 addresses and autonomous system numbers ASNs. 

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These lists contain all the IP address ranges and ASNs in blocks that are allocated for use on the Internet. It delegates allocations of IP addresses to regional Internet registries (RIR). Each RIR is responsible for allocating IP addresses for a different part of the world. 

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The second category is the Domain Name System (DNS) root zone. The DNS is a hierarchical distributed database that links domain names to IP addresses. This is then used to send data between computers. In simple terms, the DNS is used to convert human-readable domain names to machine-readable IP addresses.  

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The best analogy to understand how the DNS works is to look at a phonebook. Like a phonebook has the names and numbers of telephone users for a specific area, the DNS has the domain names and IP addresses for websites.

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And IANA maintains the top level of this database, the DNS root zone. This contains pointers where information about second-level domains can be found.

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Thirdly, IANA also manages protocol parameters. These protocols are necessary to make sure that computers understand each other when communicating over the Internet. 

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The IETF, as part of their technical protocol standards, defines these protocol parameters. IANA maintains and publishes these registries, and the information can then be used by software developers to ensure stable and predictable communications over the Internet.