When you go to a website, the website server keeps track of what you are doing on the website. This is called logging. The server keeps track of things like what page you went to, what you clicked on, and what browser you are using.
The common log format is just a fancy way of saying that the server writes down this information in a specific way that's easy for computers to read. It's like writing down information in a special code that only computers can understand.
The common log format is a simple formula that the server uses to write down information. It writes down the date and time you visited the website, your computer's IP address (which is like your computer's phone number), the type of file you accessed (like an image or a video), and what browser you used.
This might seem like boring information, but it's actually really important. It helps website owners see which pages are popular, what people are interested in, and what problems they might be having on their website. They can use this information to improve their website and make it better for everyone.
So next time you visit a website, remember that the server is watching you, but it's all for a good cause!