The SVGAnimatedEnumeration interface describes attribute values which are constants from a particular enumeration and which can be animated.
SVGAnimatedEnumeration
MDN Reference
The animVal property of the SVGAnimatedEnumeration interface contains the current value of an SVG enumeration. If there is no animation, it is the same value as the baseVal.
animVal
The baseVal property of the SVGAnimatedEnumeration interface contains the initial value of an SVG enumeration.
baseVal