stdin stands for "standard input," which is a way for a computer program to receive data from the user or another program. It is commonly used in command-line interfaces, where users can type commands or provide input directly. This input can come from a keyboard, a file, or even another program's output. In many programming languages, stdin is accessed through specific functions or libraries. For example, in Python, the `input()` function reads data from stdin. This allows developers to create interactive applications that respond to user input in real-time, enhancing the overall user experience.