# Blockchains A blockchain is an immutable (permanent), *decentralized* record of transactions. All cryptocurrency transactions are recorded and stored in a public record that everyone can view and no one can change. More specifics on how blockchains work can be explained in this [video](https://www.youtube.com/watch?v=kHybf1aC-jE\&list=PLHx4UicbtUoYPDWk2aUwZoVKMkdRKtKWe\&index=7). What is important to know as a new user is that each blockchain is slightly different from each other. Transaction speed and *gas fees* (see glossary for definition of italicized words) differ per chain as well as the *dapps* and cryptocurrencies that are native to the chain. The first step is to decide what blockchain to use. For each blockchain, it is important to consider their longterm goals, the volume of people on the chain, the dapps on the chain, the gas fees, and the transaction speed. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://dantheman8300.gitbook.io/beginners-guide-joining-the-world-of-blockchain/blockchains.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.