Rust: What is the difference between std::io and tokio::io?

1// std::io: blocking
2use std::io::Read;
3std::fs::File::open("file.txt")?.read_to_string(&mut buf)?;
4
5// tokio::io: async
6use tokio::io::AsyncReadExt;
7tokio::fs::File::open("file.txt").await?.read_to_string(&mut buf).await?;