This block introduces the fundamentals of digital video before diving into codecs and compression. Readers learn what a video frame is, how resolution and frame rate affect visual quality, how pixels and subpixels form an image, and why digital video depends on concepts like sampling, color spaces, chroma subsampling, bit depth, gamma, and HDR. The goal of this block is to give readers a clear technical foundation. By the end, they will understand the basic properties of video files and be able to read video specifications with confidence: 4K, 60 fps, 10-bit, 4:2:0, BT.709, HDR10, progressive scan, and other common terms will no longer feel abstract.