Deno API, which comes bundled with Deno and is present globally, always, without importing: https://doc.deno.land/deno/stable. Includes basic stuff like stdin, stdout, stderr, file management... etc and standard Web APIs like Fetch API, web assembly interoperability, localStorage, FormData, TextEncoder/TextDecoder, etc.
Deno std lib, an official library that presents what you could expect from a standard library, based on Deno API: https://deno.land/std@0.120.0, but you need to import it, because it's no different than any other module in the wild. Mime types, more encoding options, extended file system management, etc.
