Standard sonar sends 1 single frequency at a time. Since the only feedback is from this 1 single frequency, there is little information to work with, limiting the clarity and resolution available with standard sonar.
Instead of sending just 1 single frequency, CHIRP sends a continuous sweep of frequencies ranging from low to high. CHIRP sonar technology then interprets frequencies individually upon their return. Since this continuous sweep of frequencies provides CHIRP with a much wider range of information, CHIRP sonar is able to create a much clearer, higher resolution image.