Visual identity system
Everything that makes your stuff look like yours: mark, color, type, imagery, layout, and graphic devices, built as one coordinated kit.
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What it is
The logo is one part. The system is everything that coordinates around it: mark and its variants, a color palette with assigned roles, a type hierarchy, an imagery treatment (photography style, illustration style, crops, filters), a layout grid, and signature graphic devices like a supergraphic or pattern. A good one makes a business card, a deck slide, a job posting, and an app screen read as the same company even when the logo is nowhere on the page. The NASA Graphics Standards Manual, Unimark's American Airlines work, and Paula Scher's Public Theater identity are the canonical study pieces.
Reach for it when your output has stopped looking related to itself: every deck a different blue, every landing page a different heading font. That is a systems problem, not a logo problem, and redrawing the logo will not fix it.
Gotcha: a system is judged by the ugliest artifact anyone can build with it. Test it on the hostile applications (a dense spreadsheet, a one-color invoice, a 44px app icon, a slide with 300 words on it), not just the poster mockups. Note the naming collision too: a design system is the product-side system (principles, tokens, patterns, documentation, governance, and the design assets themselves, with code as one possible implementation rather than the whole thing), while a visual identity system is the brand-level rules a design system inherits and applies.
Ask AI for it
Design the overview board for [BRAND] using [AUDIENCE], [POSITIONING], [3 BRAND TRAITS], [EXISTING MARK], and [SPECIFIC VISUAL REFERENCE OR MATERIAL/ERA ANCHOR]. Derive every part from those inputs and say which input drove which decision: a color palette with defined roles (primary, secondary, neutrals, one accent) and hex values, a type hierarchy showing display, heading, body, and caption with real sample text, an imagery treatment (state the photography or illustration direction), a layout grid, and one signature device. Then apply the system to four artifacts: business card, slide, app screen, and social post, so the family resemblance is visible without relying on the logo.