Before the creation of the telephone or the telegraph, information that needed to be sent from one end of a country to the other necessitated a messenger to quickly deliver physical mail. In the United States for almost two years, this was achieved through the Pony Express. A relay of horse riders could deliver mail from New York to California in about ten days, but the telegraph all but made the practice 100% obsolete.
The telegraph itself had several problems, as it required the learning of Morse code between operators and a large amount of hand-work. This limited the amount of messages that could be sent, as well as the cost per message, due to the speed limitations of the sender and the receiver. When Alexander Graham Bell got the first patent for the electric telephone, it allowed for communication to explode to new heights.
Work on a harmonic telegraph was done by multiple inventors, including Thomas Edison and Elisha Gray. Both of them actually have multiple patents that pertain to the technology, but Alexander Graham Bell was the first to patent a device that we can identify to be a telephone. Italian inventor Antonio Meucci also had made breakthroughs himself even earlier, and sued Bell after his initial success. Unfortunately, he passed away due to illness before the lawsuit culminated in any legal action.
In comparison to the phones we use today, physical units used a wide variety of different methods to actually capture and replay sound, but the transmittal of those signals were the same. Bell later expanded on his creation to invent the photophone, the first device to send an audio signal wirelessly over light. Along with advancements in wireless telegraphy, these ideas were what led to the creation of the radio, and future wireless communication technologies.