A more thorough explanation:

An informal acknowledgment is a recognition or acceptance of something without following a formal process. It can refer to:

• Acknowledgment: A recognition of something as being factual or an acceptance of responsibility.
• Receipt: The act of making it known that one has received something.
• Paternal Acknowledgment: A father's recognition of a child as his own without a formal, written declaration.

For example, if someone thanks you for helping them, and you say "no problem," that is an informal acknowledgment of their gratitude. Another example is when a father treats a child as his own, even if he hasn't signed a formal document declaring paternity.

Informal acknowledgment is different from formal acknowledgment, which involves a written or legal process. For instance, a notary public may certify a document's authenticity by verifying the signer's identity and signature.