It's explained in the Learning Center (see linked pages for details on the algorithms):
Candle Chart (ToS)
Candle chart is represented by a candle-shaped bar. Top and bottom sides of the bar indicate the high and low prices on the aggregated period. The lower and the upper sides of the candle body are used to indicate the open and close prices respectively.
Candle chart considers open and close price values only on the current aggregation period when applying colors.
vs
Candle trend Chart (ToS)
Visually, Candle trend chart is a complete copy of the Candle chart. However, their coloring algorithms are different: Candle trend chart considers open and close price values on the current aggregation period and on two adjacent aggregation periods when applying colors.