Just think of it like this. This is a very basic way of thinking and technically the wording is not right but should help to understand.
First dont worry about why its moving or what’s moving it. It doesnt matter. Forget the term overbought, oversold.
The rule: The oscillator (rsi, stochastic etc) follows price. So when price goes up the oscillator goes up, price down oscillator down. That’s it, just remember that.
The oscillator has a range of 0 to 100. So as price increases the oscillator goes up towards 100. Down goes towards 0.
Therefore, when you look at a chart if price makes a high (a new peak), you would expect the oscillator to go up and make a peak. When price goes down, the oscillator goes down. When price then makes a new high (higher than previous peak) the oscillator should also make a higher peak on its chart. That would be normal.
When this does not happen: this is called divergence ie the indicator is diverging from the price action. It is abnormal to our rule.