What means relu cuts off?

Course Q&A Machine Learning Specialization Advanced Learning Algorithms
1

Hi! Didn’t understand what is on screen

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Looks like that I didn’t understand at all this lab and how it works. I understand only that ReLUs from different layers are summerized as separate parts of graphics and influence on each other. But how exactly?

2

The output of a ReLU unit is zero for negative values, and is equal to the input for positive values.

“cuts off” just means that the ReLU unit is outputting 0 because its input is negative.