Cascade means style properties are inherited by all of an element's descendants by default. Not all and not all the time, as there are necessary exceptions and other factors. The rest comes down to specificity of rules. Rules that are more specific override properties from less specific rules. Similarly, rules evaluated later override earlier rules of the same or lesser specificity. The fundamentals of specificity increase are: element type -> class -> id -> inline style. Note that the way specificity works suggests that your CSS should start vague and become more specific. There's a lot more, but those basics will get you pretty far. More on reddit.com

CSS stands for Cascading Style Sheet. I can understand the meaning of Style. Does Sheet mean “a piece of paper?” What’s the meaning of cascading? More on sitepoint.com

CSS is one part of the structure that makes up web programming alongside HTML and JavaScript. Imagine you are building a house. HTML is like the foundation, studs and support beams. It defines the structure of the webpage. JavaScript is like the plumbing and electrical work. It defines the functionality and interactivity of the web page. Which brings us to CSS. You can think of it like the tile floors, paint, shingles, etc. of the house. It defines the way the web page looks. It defines colors, shapes and sizes of elements on the page and the like. The term "Cascading" refers to the fact that the same styling rule can be applied to an HTML element at multiple scopes. For example, you may set the background color of an element directly on the HTML tag itself, then again in a style tag within the HTML file, and once again in an external CSS file. The browser must then determine which of these rules to use. Typically, this is the style defined at the most narrow scope meaning the style directly on the HTML tag itself is the one that renders. The style rules can be described as "Cascading" from the broadest scope (an external CSS file) to the most narrow (any inline CSS) with the narrowest rules taking precedence. More on reddit.com

HTML defines content, CSS decorates it and helps tell how it is displayed.

CSS stands for Cascading Stylesheet. This means that there is a hierarchy of style attributes overwriting other attributes that affect the same elements.

Think of it like this. Bob Ross does an oil painting and starts off with a canvas covered in liquid white. This is the lowest level on the hierarchy. It applies to the entire body of the painting, like a class applied to the body tag.

On that he paints some divs of class "mountain". The mountain class has the attribute paint-color:Van Dyke Brown. Since the div is within body the paint-color:Van Dyke Brown attribute overwrites the liquid white and you see the Van Dyke Brown over the liquid white.

He adds some divs of class "happy little tree" which are growing wherever they like, which happens to be on the mountains, so these happy little tree divs are within the mountain divs. Their paint-color:Sap Green is within the mountain div, so where the happy little tree divs are is painted with Sap Green on top of the Van Dyke Brown mountains.

Then Bob adds another happy little tree div. This one he wants to be Alizarin Crimson because its his world and it can be whatever fucking color he god damn pleases. Rather than giving it a special id and using the # selector Bob makes the happy little accident of using an inline style. This overwrites the happy little tree class's paint-color:Sap Green attribute with an inline paint-color:Alizarin Crimson because inline styles cascade over classes.

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