Find pixels with highest value in their local surroundings, so called maxima. Output of this node is a binary image with the found pixels in white (value 1). When using the option "Output with Tolerance Areas", the output binary image will not only contain one highest value pixel in its area, but also all other pixels which have the same value (affected by "Noise Tolerance"). Otherwise these pixels positions are averaged to one pixel which will be marked in white (value 1).

To find minima instead, you might want to invert the input.