The fs (File System) module in Node.js lets you work with files on your computer. You can use it to read, write, delete, or modify files.

When working with files, you often need to choose between synchronous and asynchronous methods.

• Synchronous file operations, such as fs.readFileSync, block the execution of your program until the file operation completes. This means that no other code runs while Node.js is reading or writing the file, which can slow down your application if the file is large or if you perform many such operations;
• Asynchronous file operations, like fs.readFile, do not block the program. Instead, you provide a callback function that runs once the operation finishes. This allows Node.js to continue executing other code while it waits for the file system, making your applications more efficient and responsive, especially when dealing with many files or slow disks.