A telephone is a device that allows people to communicate with each other over long distances using electrical signals. It converts sound waves from a person's voice into electrical signals, which are then transmitted through wires or wirelessly to another telephone. The receiving telephone converts these signals back into sound, allowing the person on the other end to hear the speaker. Invented in the 19th century, the first practical telephone was developed by Alexander Graham Bell in 1876. Since then, telephones have evolved from simple landline models to advanced mobile phones, which offer additional features like texting, internet access, and various applications.