Asked about What the hardware is doing

Why are GPUs used for deep learning?

An answer that works

The core operation is matrix multiplication, which is thousands of independent multiply-accumulate operations. A GPU has thousands of simple cores suited to exactly that, while a CPU has a few complex ones.

Reading an answer is not being able to give one. The section that teaches this is What the hardware is doing, 5 hours of GPUs & accelerators.

Learn this properly