Let's bring a concrete example. We need an animated rotating circle, as follows:
Some of our options are:
1 Put the circle on the billboard, write a script to rotate the billboard.
2 Use an animated gif as the source.
3 Do the whole thing in a shader, which allows 2 different options:
- Rotate the billboard in the vertex shader
- Draw the rotating circle in the fragment shader based on current time.
In 1. someone needs to write that script, which is some kind of programming task that has to do with graphics. For 2. we don't need a programmer, unless the engine - like most - doesn't support import of animated gifs, in which case somebody needs to program that part. In 3. someone has to program the shader, which could be an artist or a programmer.