Think of middleware as the plumbing or the middleman of software applications. It is software that sits between two different applications, tools, or components to help them communicate and share data seamlessly. Common examples include: 1. Authentication & Authorization: Checking if a user is logged in before letting them see their profile. 2. Logging: Recording every request that comes into the server for debugging purposes. 3. Body Parsing: Converting incoming raw text/JSON data into a clean object the code can easily read. 4. CORS (Cross-Origin Resource Sharing): Managing which websites are allowed to talk to your API.