user7939: 
An asset is uniquely identified by an asset ID, which is a pair of both the policy ID and asset name.

The Policy ID is a hash of the monetary policy script that was used to mint the token. What prevents someone from minting more of the same tokens using the same policy script?

user28: One part of the policy is usually about signatures associated with it.
If you want to use the same script again, you will need the corresponding private keys.
If you have them and policy permits it, you can mint more tokens.
This is very important, as if your "NFT project" does not have a policy that prevents them to
mint more tokens, it is really unfair to claim one as such.

7939: <blockquote>
<p>An asset is uniquely identified by an asset ID, which is a pair of both the policy ID and asset name.</p>
</blockquote>
<p>The Policy ID is a hash of the monetary policy script that was used to mint the token. What prevents someone from minting more of the same tokens using the same policy script?</p>
 28: <p>One part of the policy is usually about signatures associated with it.</p>
<p>If you want to use the same script again, you will need the corresponding private keys.</p>
<p>If you have them and policy permits it, you can mint more tokens.</p>
<p>This is very important, as if your &quot;NFT project&quot; does not have a policy that prevents them to
mint more tokens, it is really unfair to claim one as such.</p>
