Are you using more than one language on your Mac? Have you wander what is the shortcut for switching between your keyboard language layout?
Try: cmd + space
By default, this will open the Spotlight Search. To activate this shortcuts for your language input you have to:
1. Go to System Preferences -> Language&Region
2. Then “Keyboard preferences…”
3. Go to “Shortcut” tab and then “Input sources”. Check the shortcut options.
4. An warning will show “Shortcut used by another action”. That’s the Spotlight search. Go to “Spotlight” and uncheck the shortcut option.
That’s all. Now you can use the cmd+space shortcut to easily switch between input language. Have fun!