Explain readFile and createReadStream in Node.js.

Both readFile and createReadStream are ways to read and execute files provided by the Node.js.

The readFile process is fully buffered which returns response(s) only if the complete file is entered into the buffer and can be read. This process is highly memory intensive and can become slow in case the file size is large. The createReadStream process is partially buffered, treating the entire process as a series of events. In this process, the whole files are split into chunks that are processed and then sent as a response individually in succession. Unlike readFile, createReadStream is effective when it comes to reading and processing large files.