The earliest recorded music, including Gregorian Chant, had a monophonic texture, meaning it subsisted solely in a single melodic line.
High Medieval and Renaissance music tended to have a polyphonic texture, with multiple melodic lines interacting harmonically.
In the Baroque Period, a new way of looking at harmony developed. A melodic part would be set above a chord, which composers began to think of as a single unit, rather than three separate parts interacting polyphonically. This chord-based texture with a clear separation between melody and harmony is called a homophonic texture, and it revolutionized music all the way down to today.