Oscillators are in a general sense indicators that are used to determine whether the market has gone too far in one direction. They may be bounded, having possible values only with a specified range, or they may be unbounded, being capable of taking on any value. For all practical purposes, just about any measure of price can be turned into an oscillator by a rather simple mathematical transformation. Unfortunately, the overriding probem with indicators is what period to use in calculating them: too fast a period and you get whippy choppy action that reacts too fast and leaves you breathless with its switches in direction; too slow a period, and the oscillator lags so much that the action it portends is already over, by the time that it signals the action.
How about if instead of trying to determine that best period for the oscillator, we let the market tell us? Instead of specifying a period, we shall just use the market's dominant cycle period or a suitable fraction thereof, half or quarter, if we need zippier action. Many pundits claim that the correct period to use for an oscillator is half the period of dominant cycle, if such can be determined. That is the default that we usually use. Check out the indicator, and you will see how you can change that.