Explanation:

The Salesforce Lightning Design System (SLDS) reflects the patterns and components that underpin the Salesforce product. These patterns and components provide a unified language and consistent look and feel when designing apps and products within the Salesforce ecosystem. The Lightning Experience UI, which SLDS represents, was crafted using four core design principles. We encourage you to keep them in mind as you develop your applications. They are:

Clarity — Eliminate ambiguity. Enable people to see, understand, and act with confidence.
Efficiency — Streamline and optimize workflows. Intelligently anticipate needs to help people work better, smarter, and faster.
Consistency — Create familiarity and strengthen intuition by applying the same solution to the same problem.
Beauty — Demonstrate respect for people’s time and attention through thoughtful and elegant craftsmanship. References: Introduction to the Salesforce Lightning Design System.