One of the most important differences between the centralized web and the decentralized web is the way we identify and retrieve data on each.
URLs (Uniform Resource Locators) are the primary addresses we give each other for data on the centralized web (you know, that plain old web we're all used to).
Cryptographic hashing is the most important tool in the toolbox of decentralized data structures.
One of the most important features of the web—whether centralized or decentralized—is linking.
For cryptographic hashing to work, we need to know what data format we're working with and use an appropriate tool.