When the sound waves of your voice move the diaphragm, it moves the magnet inside the coil. The movement creates a small electric current which is then transferred along the wire. Different sound waves cause different amounts of current. A loud voice moves the diaphragm more, which moves the magnet more, which causes a stronger current. As your voice changes in loudness and inflection, different amounts of current are sent along the telephone wire as electric signals.
All modern communications depend on electric signals.
Sound and pictures are changed into signals and sent along wires. At the other end of the wires, the signals are received and changed back into sound and pictures. Sending signals along wires works fine as long as you don't have to send signals too far. When wires cannot be used, the signals are sent through the air by electromagnetic waves. The waves travel in straight lines from a sending antenna to a receiving antenna.