A digital radio encodes the analog voice frequencies into a digital data stream and sends it out using digital modulation of the radio. An analog radio simply sends out the voice frequency directly by modulating the analog radio signal.
Well digital radio is where you speak into the microphone and the radio turns your voice into numbers and digits and sends those digits over the air. Then another radio receives those digits and converts them back into audio that you can understand. - Analog radio on the other hand simply transmits your voice out over the air without changing it into digits and numbers. Another radio receives your voice without having to do any kind of conversion as it is simply "analog". Not sure if this explains your question but basically digital is where your voice gets converted into numbers and then converted back to voice at the other end. Basically the digital radio has a computer to process your audio. Where as analog does not. It just uses a transmitter and receiver to send your voice over the air. Out of these two types analog is superior and more reliable.