This is the core of any GSG. It covers which version of your logo gets used where, how much space needs to surround it, the minimum size it can appear at before it becomes illegible, and what you're not allowed to do with it. That last part, the improper use section, is more useful than most people expect. It's a specific list of things like don't skew it, don't change the colors, don't put it on a busy background, don't add a drop shadow. Sounds obvious until you've seen a vendor do all of those things because nobody told them not to.
The color section documents every approved color in your brand, with the exact values for each format. HEX for digital, CMYK for print, RGB for screens, and Pantone for reference. Pantone is a standardized color matching system that gives you a universal reference point regardless of who's printing or producing your work. A print shop in another city running your job on a different press can match your brand color exactly if they have the Pantone value. The guide takes the guesswork out of the equation for anyone producing work on your behalf.
The fonts section documents which typefaces are approved for use and in what context. Usually there's a primary font for headlines and a secondary font for body copy, and the guide specifies which is which. This matters more than people expect. Fonts have a personality and that personality contributes to how your brand feels. Using the wrong one, or letting someone substitute a system font because they didn't have access to the right one, is one of the quieter ways a brand starts to look off.
A foundational GSG covers everything above. A fuller brand package adds sections on mission, vision, values, positioning, and tone of voice. Those sections are less about how the logo gets used and more about how the brand thinks and communicates. Not every project needs that level of detail, but when it's there it gives everyone working on the brand a much clearer picture of what they're working toward.
If you want to understand why any of this matters in the first place, part one covers it.
