GUI testing VS android GUI testing VS CLI testing

i'm studying on GUI testing in android platform.

Testing have existed for very long time, and GUI testing, especially in android is quite new one.

I want to know what are the differences between those 3 testings, GUI, android GUI and CLI(command line interface).

I already read the GUI testing in wikipedia, but couldn't understand why GUI testing has scaling problem and also more operations to be tested than CLI testing.

Thank you in advance.