Stochastic Oscillator crossovers?

i just watched the trading 212’s “Stochastic Oscillator explained” and when it mention’s crossovers.
what is the K% and the D%? is it the overbought or oversold?

Maybe this helps. See:

To ,make sure i know what i am talking about …

K% is the current value of the share

D% is the average price of K% (over a period of time?)