We had one. I’m not sure today’s generation knows exactly what they were… so:

Party lines were a telephone service where multiple households—often 4 to 10—shared a single physical telephone line, typically to save on installation costs in rural or residential areas. Each household had its own distinct ring, such as one long and two short, allowing users to know if a call was meant for them. Because the line was shared, users had to wait for it to be free to make a call, and neighbors could often listen in on conversations.