Sticky Keys

Sticky Keys is an accessibility feature designed to assist users who may have difficulty holding down multiple keys at the same time. Sticky Keys make keyboard shortcuts more accessible for individuals with limited dexterity. It lets you use the Shift, Control, Alt or Windows Logo keys by pressing one key at a time.
To activate Sticky Keys, press Shift five times in quick succession. This will bring up the Sticky Keys confirmation dialog. Press Enter on the Yes button to enable, or Escape to cancel.
To turn off Sticky Keys, press Shift five times again. You’ll see the same confirmation dialog, but this time Tab to the No button and press Enter, or press Escape to cancel.
Sticky Keys can also be switched on/off and adjusted in the Accessibility settings (Windows + U). For example, you can disable the sound that is played when keys are pressed and released.