The unmodulated carrier is simply the electricity your phone operates on, the steady and continuous current your telephone company provides. It carries the conversation. When you talk the phone impresses your conversation on the current the telephone company supplies. Conversation causes the current's resistance to go up and down, that is, your voice varies or modulates the carrier, the electricity operating your phone. Below is a simplified view of a digital signal.
Current goes on and off.
No wave thing. There was no chance the Reis telephone could transmit intelligible speech since it could not reproduce an analog wave, not by making and breaking a circuit. It was not until the early 1960s that digital carrier techniques simulated an analog wave with digital pulses. Even then this simulation was only possible by sampling the wave 8,000 times a second. In these days all traffic in America between telephone switches is digital, but the majority of local loops are analog , still carrying your voice to the central office on a modulated wave.