Some laptop keyboards has built-in numeric keypads. This can be activated and deactivated only using key combination in keyboard.
If you're writing numbers instead of letters when you press the keyboard of your laptop and you must hold down the Function key (Fn) to write normally.
This is due to the fact that the digital lock is activated. To solve this, simply press the Fn+Numlk or depending of the model, press the button or Fn + Shift +Numlk.
Hope this helps,
Delmar