Both readFile and createReadStream are used to read the contents of a file in Node.js, but they have some differences in their usage and behavior.

readFile is a method of the fs (File System) module in Node.js that reads the entire contents of a file into memory and returns the data as a Buffer or string. It is a synchronous method that blocks the event loop until the file is read completely. It is suitable for reading small files, as it loads the entire file into memory at once, which can cause memory issues for larger files.

createReadStream, on the other hand, is an asynchronous method that creates a readable stream of a file. It reads the contents of a file in chunks, rather than loading the entire file into memory at once. This method is suitable for reading large files, as it allows you to read data from the file in smaller chunks and process it incrementally.

Another difference between readFile and createReadStream is how they handle errors. readFile throws an error if there is any issue with the file system or if the file is not found. createReadStream, on the other hand, emits an error event that needs to be handled separately.