What actually is rock music?

Rock music, or rock, serves as an umbrella term for musical styles that have developed since the late 1960s from the mixing of late 1950s and early 1960s rock ’n’ roll with other musical styles such as the blues.
Since then, the new musical style — which would have been unthinkable without its electric amplification — required that entirely new instruments be invented. The innovator Leo Fender invented the first solidbody electric guitar with the Telecaster in 1950, reducing the annoying feedback that had been a constant problem with guitars with full resonant bodies. In 1951 he set another milestone with the first electric bass. Gibson quickly followed in 1952 with the Les Paul models and in 1961 with the simpler SG models. Jim Marshall provided the necessary volume from 1962 onward with his amplifiers and speaker cabinets, produced in England. Ernie Ball replaced the makeshift banjo strings that had been used up to that point with thinner, easier-to-play strings that were now produced specifically for electric guitars and basses.
Over the decades, rock music has constantly changed and evolved. For example, numerous subgenres such as alternative rock, grunge and punk emerged, which became particularly popular in the '90s and 2000s.