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From Wikipedia:

Composite (number)
A composite number is a positive integer that can be formed by multiplying together two smaller positive integers. Equivalently, it is a positive integer that has at least one divisor other than 1 and itself. Every positive integer is composite, prime, or the unit 1, so the composite numbers are exactly the numbers that are not prime and not a unit.

It's not a math question. It's a question about a word. No different than if you asked, as in another question I read today, what legislation and autonomy are. Those are words about concepts in law or political science. But asking about their meanings isn't a question of law or political science.

The word is net.

I'm a maths teacher, and this is the standard term used in Australia. I'm fairly sure it's the same in other parts of the English-speaking world, thanks to sources like:

• Wikipedia
• Wolfram MathWorld

It's worth noting that this is not a common thing for most people to talk about, and unfortunately, "net" also has other (more common) meanings. A descriptive phrase, like your "unfolded thing", would be useful to name it when talking to people unfamiliar with the correct name.