What it does
I'm not aware of an official Magic: The Gathering keyword or ability called "Cura." It's possible this is a misspelling, a card name, or a term specific to a custom/unofficial set (like one you might find on a homebrew platform such as Mythicwyrm).
A few possibilities you might mean: "Cura" could be confused with "Cycling," "Convoke," or perhaps a card with "Cura" in its name. It might also be a custom mechanic from a fan-made set, in which case its rules would be defined locally rather than in the official Comprehensive Rules.
If you can share the card text or where you encountered "Cura," I can explain exactly how it works, the rules nuances people misplay, and how it matters in Commander. I'd rather give you accurate information than invent rules for a term I can't verify.
Iconic cards with Cura
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