This is similar to how high the waves are coming into shore from the ocean. The bigger wave has a higher amplitude. The other thing is frequency. Frequency is how often the wave occurs at any point. The faster the wave repeats itself, the higher the frequency.
Frequency is measured by the number of times in a second that the wave repeats itself.
Old timers remember when frequency was described in units of cycles per second. Metric prefixes are often used, so that 1000 hertz is a kilohertz, one million hertz is a megahertz, and so on. The important thing in any communications system is to be able to send information from one place to another. This means we have to find a way to impress that information on the radio wave in such a way that it can be recovered at the other end. This process is known as modulation.