Pico CSS is a minimalist CSS framework designed to make HTML elements responsive and elegant by default. It prioritizes semantic HTML and requires very few CSS classes.

Key features and functionalities of Pico CSS include:

• Semantic HTML: Pico directly styles HTML tags, using fewer than 10 CSS classes. It also offers a class-less version for those who prefer pure HTML.

• Pure CSS: It achieves elegant styles with pure HTML markup, without dependencies, package managers, external files, or JavaScript.

• Responsive Design: Pico natively scales font sizes and spacing with screen widths, providing a consistent look across devices without extra classes or configurations.

• Color Schemes: It includes light and dark color schemes that automatically adapt to users' prefers-color-scheme, without using JavaScript.

• Customization: Pico can be customized using over 130 CSS variables, or through SASS. It includes 20 color themes and over 30 modular components.

• Performance: Pico keeps HTML lean, decreases memory usage, avoids excessive CSS specificity, and reduces the number of loaded files. It is designed to be faster than bulkier frameworks.

• Simplicity: Pico emphasizes simplicity and ease of maintenance.

• Installation: Pico requires only the addition of its CSS file to your HTML.

In contrast to more complex frameworks, Pico CSS aims to provide a strong design foundation through simplicity. It uses a minimal approach to styling, making it a good starting point for a clean and lightweight design system. The framework is designed to be easy to use, with styles applied directly to HTML elements, reducing the need for extensive class overrides. An example of a form styled with Pico CSS involves using standard HTML elements such as <form>, <input>, and <button>. In contrast, an example of a form using a Utility CSS Framework has multiple div tags with various classes.