Have you been using your computer and somehow you managed to lock your keyboard? How do you unlock it? You can try pressing the following keys on the keyboard all at the same time.
ctrl+alt+shift+del
You can also try turning off the “Num Lock” key, by pressing if it still works.
If that doesn’t fix the issue I assume the keys on the keyboard stopped working. Do any keys work? Is it a USB keyboard or PS2? Also, if it’s a non standard keyboard with programmable keys then perhaps one of the keys accidentally locked it.
A bottom line solution is to turn off the computer, disconnect the keyboard, restart the computer and after boot, reconnect the keyboard so that the operating system would recognize it as new hardware.