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What are neural networks & how do they learn?

## What are NN? (19 min)

3Blue1Brown by Grant Sanderson has a series of 4 videos on neural networks which is easy to watch, fun, and does an excellent job at introducing the functioning of a simple neural network.

For this lesson, you will watch the first of these videos which explains what NN are.

Watch it beyond the acknowledgement fragment as the function ReLU (a really important function in modern neural networks) is introduced at the very end.

As you develop your own ML models, if you find that your mathematical background is shaky, 3blue1brown also has an excellent series of videos on linear algebra and an equally great one on calculus.

## How do NN learn? (21 min)

In this lesson, you will watch the second video on NN by 3Blue1Brown which explains how neural networks learn.

## What is backpropagation? (14 min)

In this lesson, you will watch the third video on NN by 3Blue1Brown which explains how backpropagation works.

There is one minor terminological error in this video: they call the use of mini-batches **stochastic gradient descent**. In fact, this is called **mini-batch gradient descent**. Stochastic gradient descent uses a single example at each iteration.

## How does backpropagation work? (10 min)

In this lesson, you will watch the last video on NN by 3Blue1Brown which dives into the calculus of backpropagation.