There are many resources online that give an introduction into how Bitcoin and other blockchain-based systems work under the hood. Each has its own unique perspective and focus. Our approach here is to look at it all in terms of layers. We also simulate a miniature blockchain network for you - in your browser, right now! It is a close enough model of Bitcoin, and you are invited to interact with it!
This page here shows you all layers at once. This is a lot of information! Try exploring one layer at a time. By clicking on a layer name (the labels with a +) you can open some explanatory text about that layer. Also try clicking or hovering around the visual elements - many of them are interactive! You can control the speed of the simulation via the time controls way below.