VFX stands for Visual Effects. These are the imageries which are created in post-production. In essence, they are an image that appears in a film that could not be photographed during primary cinematography for whatever reason. Examples of VFX would be fantastical creatures whose physiology makes it impossible to create them via a “man in a monster costume”, sets that are too large and expensive to build physically or stunts that are so dangerous it’s safer to produce them in post-production via various means.
Post Production Institute's blog
What are symbols in Adobe Illustrator?
A symbol is an object that we can use in a document multiple times. Not only this but a symbol can even be created in illustrator. For example, if we create a flower symbol, we can add that same symbol multiple times in a single artboard. A symbol can even be modified in Adobe Illustrator.
Uses of symbols
Using symbols can save time and can reduce the file size greatly because we can add a symbol multiple times to our artwork without actually adding the object multiples times.