# How many types of API functions are there in
Node.js?

There are two types of API functions in Node.js:

* **Asynchronous, non-blocking functions** use the callback pattern, in which a callback function is passed as an argument to the function and is executed when the function completes.
    
* **Synchronous, blocking functions** have a `Sync` suffix in their name, such as `fs.readFileSync`