In the process of stock price fluctuation, the K-line chart shows that the stock price keeps falling, but the technical indicators keep rising, which is the bottom deviation. Simple illustration, taking macd as an example, when the stock price falls, its macd index rises, so we can call it bottom deviation.
Top deviation (contrary to bottom deviation) is the phenomenon that the stock price keeps rising on the K-line chart, but all technical indicators are falling upward, which is called top deviation. Simple illustration, taking macd as an example, when the stock price goes up, but its macd goes down, we can call it top deviation.