Selectors: CSS3 introduced new and more powerful selectors, allowing for more precise targeting of HTML elements. This includes attribute selectors, pseudo-classes, and pseudo-elements.

Box Model: CSS3 allows for greater control over the box model, which defines how elements are sized, spaced, and positioned. You can use properties like box-sizing to control how padding and borders affect the total size of an element.

Transitions and Animations: CSS3 introduced transitions and keyframe animations, making it easier to create smooth animations and transitions between different states of an element.

Gradients: CSS3 allows you to create gradient backgrounds, including linear and radial gradients, without the need for images. This feature provides more flexibility in designing backgrounds.

Shadows: You can use CSS3 to add box shadows and text shadows to elements, which can enhance the visual appeal and depth of your designs.

Border Properties: CSS3 introduces more advanced border properties, such as rounded corners (with border-radius) and multiple borders (with border image).

Flexible Box Layout (Flexbox): CSS3 introduces the Flexbox layout model, which makes it easier to create complex layouts with elements that automatically adjust to various screen sizes and content.

Grid Layout: CSS Grid Layout is another layout model introduced in CSS3, which provides a two-dimensional grid system for creating complex layouts with precise control over rows and columns.

Media Queries: While media queries were initially introduced in CSS2, CSS3 expanded on this concept. Media queries allow you to apply styles based on the characteristics of the device or viewport, making it possible to create responsive designs for different screen sizes and devices.

Custom Properties (Variables): CSS3 introduced custom properties, also known as CSS variables, which allow you to define reusable values and apply them throughout your stylesheet.

Font Features: CSS3 provides more control over fonts, including the ability to use web fonts (with @fon-face) and apply advanced typography features like ligatures and font variations.

Filters and Blend Modes: CSS3 allows you to apply visual effects to elements, such as blurring, color adjustments, and blend modes.