Caps Lock or Caps Lock key

Caps Lock refers to the Caps Lock key that is often located at the far left side of the keyboard, usually just above the Shift key.

Pressing the Caps Lock key should cause a LED to become lit somewhere on the keyboard, often above the number pad.

When the Caps Lock LED is lit, Caps Lock is turned on which means that if you type a letter without pressing the Shift Key, it will be shown as upper case.

Caps Lock can be turned off by pressing the Caps Lock key again.  The Caps Lock LED should turn off and you should be able to type normally again.