The document discusses application-specific blockchains (appchains), which are customized blockchains designed for single applications, offering benefits like scalability, customization, and improved security. It contrasts appchains with other blockchain types such as layer 1s, layer 2s, and sidechains while detailing common frameworks for their creation, like Cosmos SDK and Substrate. Additionally, it outlines examples of appchains and their implementations across different platforms including Avalanche, Polygon, and Binance Smart Chain.