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These are CSS custom properties (CSS variables) likely used by a design system or animation library to control an element’s animation. Breakdown:

• –sd-animation: sd-fadeIn;
  • Selects an animation preset named “sd-fadeIn” (a keyframes animation or a named preset the system recognizes).
• –sd-duration: 250ms;
  • Animation length: 250 milliseconds.
• –sd-easing: ease-in;
  • Timing function: starts slowly and accelerates (CSS timing-function easing).

How they’re used (example pattern):

• A stylesheet or component reads these variables and maps them to real CSS rules, e.g.:
  animation-name: var(–sd-animation);animation-duration: var(–sd-duration);animation-timing-function: var(–sd-easing);

• Or the system may translate the preset name to keyframes (e.g., sd-fadeIn → from { opacity: 0; transform: translateY(4px); } to { opacity:1; transform:none; }).

Tips:

• Provide fallback values: use var(–sd-duration, 250ms) etc.
• Combine with animation-delay, iteration-count, fill-mode if needed.
• Ensure the keyframes or preset sd-fadeIn exist; otherwise nothing will animate.

If you want, I can:

• show a complete CSS example with keyframes for sd-fadeIn,
• convert those variables into inline styles or a utility class,
• or create variants (slower/faster, different easing). Which would you like?