
Explain like I'm five
Imagine you're looking for your friend in a crowd. You don't scan every single person's face in detail; instead, you quickly glance at small groups of faces, looking for familiar features like their hair or glasses. A Convolutional Neural Network does the same with images—it looks at tiny portions at a time, learns what's important, and then combines those clues to recognize the whole picture.

Why it matters
Convolutional Neural Networks power everything from your phone's face unlock to self-driving cars spotting pedestrians. They revolutionized computer vision because they can automatically learn to detect features without needing a human to program every rule.

Common misconception
Many people think CNNs 'see' images like humans do, but they actually break the image into tiny grids and process numbers. Another misconception is that CNNs need huge amounts of data to work—they do need a lot, but modern techniques can make them effective with less.

Formal definition
A Convolutional Neural Network (CNN) is a class of deep neural networks designed to process structured grid data, such as images. It uses convolutional layers that apply learnable filters to local regions of the input, followed by pooling layers to reduce dimensionality, and fully connected layers for classification. CNNs exploit spatial locality and translation invariance through shared weights and hierarchical feature learning.