Glossary
Appchain
An application-specific blockchain — a chain built and tuned for a single app or protocol instead of competing for block space with every other use case on a shared L1.
A general-purpose chain like Ethereum packs every application into one shared execution environment, so a busy NFT mint or game can spike fees for everyone. An appchain flips that: the application gets its own blockchain, with the block space, gas token, fee rules, and validator set tuned to its needs.
The upside is sovereignty and performance — no noisy neighbors, and the freedom to change the virtual machine or governance at will. Frameworks like the Cosmos SDK, Polygon CDK, the OP Stack, and Avalanche Subnets have made launching one far cheaper than it once was. The trade-off is bootstrapping security and liquidity alone, which is why many appchains now lean on shared security from restaking or a settlement rollup.