CSS
CSS, or Cascading Style Sheets, is the stylesheet language used to control the presentation of HTML and other markup documents.
CSS rules connect selectors with declarations. It is used for typography, color, spacing, layout, responsive behavior, animation and many other aspects of visual presentation.
How presentation is attached to structure
CSS rules connect selectors with declarations. It is used for typography, color, spacing, layout, responsive behavior, animation and many other aspects of visual presentation. In practical terms, CSS belongs to the browser, server or document layer. Knowing that layer is important because it tells you what the term can change, what it cannot change, and where to look when something behaves unexpectedly.
A rule changing a card without touching its content
A rule such as .card { padding: 24px; border-radius: 16px; } changes presentation without changing the card’s HTML content.
Where the cascade becomes visible
You do not need to memorize the term in isolation. It becomes useful when you can recognize it in the tool, browser, file or conversation where the concept is doing real work.
CSS is not the same thing as HTML
CSS, or Cascading Style Sheets, is the stylesheet language used to control the presentation of HTML and other markup documents. By contrast, The CSS cascade is the set of rules used to resolve which declarations apply when multiple declarations target the same property on the same element. The two can appear in the same project, but they describe different parts of the work and should not be used as interchangeable labels.
The mistake: assuming the nearest rule wins
The common mistake is to use CSS as if it also meant Cascade. That blurs two separate decisions and usually sends troubleshooting in the wrong direction. A better test is practical: Inspect the element’s matched and computed styles to see which declarations actually win.
Why styling logic matters at scale
In day-to-day work, CSS matters when you control typography, spacing, layout, color and responsive behavior. The practical value is not the vocabulary itself; it is being able to identify the right control, file, setting or decision when the concept becomes relevant.
A rule such as .card { padding: 24px; border-radius: 16px; } changes presentation without changing the card’s HTML content. That example is useful because it turns the definition into something you can recognize, test and discuss with other people working on the same project.
Related terms worth learning next
Sources and further reading
Use these references when you need documentation-level detail, specifications or product-specific behavior beyond the plain-English explanation above.