Is the principle of telephone electromagnetic wave?

The principle of telephone is to convert sound signals and electrical signals to each other. When talking, the sound signal is converted into an electrical signal, and when listening to the other person, the electrical signal is converted into a sound signal.

So how is the electrical signal transmitted?

Wired phones transmit electrical signals through telephone lines, while wireless phones (such as mobile phones) transmit electrical signals through electromagnetic waves.

Telephone lines or electromagnetic waves here are carriers for transmitting electrical signals, just like cars pulling things from here to there.