What it does
I'm not aware of "Void Shields" as an official Magic: The Gathering keyword or ability. It doesn't appear in any printed rules or card text that I can verify.
You may be thinking of a few similar-sounding things: shield counters (introduced in Dominaria United), which prevent the next instance of damage or destruction to a permanent, then are removed; or perhaps a Warhammer 40,000 Universes Beyond card with custom flavor text referencing "void shields" thematically.
If you can tell me the specific card name or set this comes from, I can give you an accurate rules breakdown of how it works, the common misplays, and its Commander relevance. I'd rather not invent mechanics that could mislead your gameplay.
Iconic cards with Void Shields
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