Triple Top is a bearish reversal pattern that leads to the trend change to the downside. Whereas Triple Bottom is a bullish reversal pattern that leads to the trend change to the upside.
A triple top is when a stock price reaches a resistance level three times in a relative short time frame and a triple bottom is when a stock price reaches a support level three times in a relative short time frame. Movement below the pullback low or above the pullback high triggers a sell or buy signal respectively.