The difference between scss placeholders and scss mixins

placeholderVmixinInput.scss

// ----
// Sass (vundefined)
// Compass (vundefined)
// dart-sass (v1.18.0)
// ----

$MYBLUEEYES: #3587DA;

@mixin card {
  border: 1px solid $MYBLUEEYES;
}

%otherCard {
  border: 3px solid $MYBLUEEYES;
}

.card {
  @include card;
}
.card2 {
  @include card;
}

.card3 {
  @extend %otherCard;
}
.card4 {
  @extend %otherCard;
}

placeholderVmixinOutput.css

.card4, .card3 {
  border: 3px solid #3587DA;
}

.card {
  border: 1px solid #3587DA;
}

.card2 {
  border: 1px solid #3587DA;
}