The `read()` function is a method used in programming to retrieve data from a file or input stream. When called, it reads the contents of the specified file and returns it as a string or bytes, depending on the context. This function is commonly used in languages like Python and Java to handle file operations. In Python, for example, you can use `read()` to get all the data from a file by opening it in read mode. You can also specify the number of bytes to read by passing an argument to the function. This makes it a versatile tool for managing file input.