What is the different between frequency and wave length of light?

In physics, the terms period and frequency are applied to things that repeat or "move in cycles" or "go around" or the like. The period is the amount of time (measured in seconds, minutes, etc.) it takes to perform one complete cycle of the object or thing being observed. The frequency is the rate (in cycles per unit of time) that the cycles are happening in.

The A above middle C often used as a reference in music equates to a string on an instrument vibrating at 440 cycles per second. That 440 cycles per second (or 440 Hertz) is the frequencyof the vibration of the string. It also follows that the string will complete one entire cycle of its range of movement in 1/440th of a second. The 1/440th of a second (0.00227272727... seconds) will be the period of that motion.