What's a chaos witch

Ask one.

Unless you're referencing the fictional boss Chaos Witch Quelaag from Dark Souls, the name really explains itself.

So what would chaotic elements be

You can always Google the word 'Chaos' and its meaning should become more clear. Then you can wonder about what the word 'Elements' means. After that make the two words into a definition.

The word comes from Greece the meaning its the void or the beggining of everything also known for the greeke god chaos

Chaos is one of the primordial elements with Darkness and Light. Notice I said "Primordial" not elemental they are different.

I didn't ask you where the word came from. Oxford Dictionary describes chaos as Definition of chaos in English:

1; Complete disorder and confusion: "snow caused chaos in the region"

It also describes chaos as

1.1 Physics The property of a complex system whose behaviour is so unpredictable as to appear random, owing to great sensitivity to small changes in conditions.

And Friendly, you don't seem to know what Light or darkness are. Darkness is simply the absence of light. And light is a form of electromagnetic radiation!

Still I'm not learning the dictionary

I assume that you mean a witch who practices Chaos Magick. There were a lot of interpretation for this path in the internet, try looking up Sigil Magick, it usually leads to more information about Chaos Magick.
Really this path is quite complex.

I found the resources list, you might want to explore it to see if this is what you are looking for.
http://thesigilworkshop.tumblr.com/post/120739768487/list-of-resources-at-thesigilworkshop