ee.ImageCollection.reduce

Applies a reducer across all of the images in a collection.

If the reducer has a single input, it will be applied separately to each band of the collection; otherwise it must have the same number of inputs as the collection has bands.

The reducer output names determine the names of the output bands: reducers with multiple inputs will use the output names directly, while reducers with a single input will prefix the output name with the input band name (e.g., '10_mean', '20_mean').

Usage	Returns
ImageCollection.reduce(reducer, parallelScale)	Image

Argument	Type	Details
this: collection	ImageCollection	The image collection to reduce.
reducer	Reducer	The reducer to apply to the given collection.
parallelScale	Float, default: 1	A scaling factor used to limit memory use; using a larger parallelScale (e.g., 2 or 4) may enable computations that run out of memory with the default.