pixel
A pixel is the basic unit of an image, and each pixel makes up an image. You can think of a pixel as a point in an image.
Let's take a visual look at how pixels make up an image. In the image below, you can see squares, which are pixels.
How many pixels does that picture have? To answer this question, another very important concept needs to be introduced - resolution.
resolution
The resolution of an image (or video) refers to the size or dimensions of the image. We generally use the number of pixels to represent the size of an image. For example, for a 1920x1080 image, the former 1920 refers to 1920 pixels in the width direction of the image, while the latter 1080 refers to 1080 pixels in the height direction of the image.
Common resolutions in the video industry include QCIF (176x144), CIF (352x288), D1 (704x576 or 720x576), and the familiar 360P (640x360), 720P (1280x720), 1080P (1920x1080), 4K (3840x2160), 8K (7680x4320), etc.
So what is the difference between the same image represented by different resolutions? We can intuitively feel it through the following set of pictures.
We can see that at 1x1 we can only see one pixel, only one color, not at all