unordered-list

Those look like CSS custom properties and a shorthand custom property likely used by a design system for animation. Briefly:

• -sd-animation: sd-fadeIn;
  • A custom (nonstandard) property naming an animation preset (here “sd-fadeIn”). Likely referenced by component styles to pick which keyframes or animation behavior to apply.
• –sd-duration: 250ms;
  • Duration of the animation (250 milliseconds). Use as animation-duration: var(–sd-duration);
• –sd-easing: ease-in;
  • Timing function for the animation. Use as animation-timing-function: var(–sd-easing);

Typical usage example:

.element {animation-name: var(–sd-animation);  animation-duration: var(–sd-duration);  animation-timing-function: var(–sd-easing);  animation-fill-mode: both;}@keyframes sd-fadeIn {  from { opacity: 0; transform: translateY(8px); }  to   { opacity: 1; transform: translateY(0); }}

Notes:

• These custom properties are purely for author convenience; browsers ignore unknown custom properties unless referenced.