What is the difference between console.readline() and console.readkey()?

The difference is that Console.ReadLine reads a line of text entered at the console when the enter key is pressed.

In contrast, Console.ReadKey just reads the next character (or function key) pressed by the user. It is not necessary to press the enter key and doing so would place a second character in the console's input buffer which could be read by a subsequent call to Console.ReadKey.