What is the use of fill

Question

the use of fill inside the animate tag in the SVG Animation

Answer 1

The fill attribute has two meanings based on the context it's used.

By default, when animation elements end their effects are no longer applied to the presentation value for the target attributes. The fill attribute can be used to maintain the value of an animation after the active duration of an animation element ends.

For shapes and text, the fill attribute is a presentation attribute that define the color of the interior of the given graphical element. What is called the "interior" depends on the shape itself and the value of the fill-rule attribute. As a presentation attribute, it also can be used as a property directly inside a CSS stylesheet.

Read more on:
https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/fill