Cascading Style Sheets (CSS) are files inserted into an
HTML document that control the appearance of web pages including layout, colors, and fonts.
CSS allows web developers to separate the structure/content of a webpage from its styling, making it easier to make changes or updates to the design without affecting the page's underlying content.
CSS can be included in an HTML document using the `<style>` element within the `<head>` section, or linked externally using a `<link>` element. CSS rules consist of a selector (to target specific HTML elements), followed by a set of properties and values that define how those elements should be styled.
CSS properties can include font properties (such as font-family, font-size, and font-weight), color properties (such as color, background-color, and opacity), layout properties (such as margin, padding, and display), and many more.
Using CSS, web developers can create visually appealing and responsive web designs that adapt to different screen sizes and devices. CSS also allows for animations, transitions, and other interactive effects to enhance the user experience on a website.