1. Layman terms - it means they plan to deny your case.
2. Follow the instructions on the notice. You may want to HIRE an attorney in preparing a thorough response. If USCIS is not satisfied with the response and/or no response received, they will deny the case, and you will likely be referred to Immigration Court. There may be additional consequences from a denial (section 203c - Marriage Fraud if marriage-based case).
Legal disclaimer: Mr. Zapata's response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Zapata's statement above does not create an attorney/client relationship.
Hire an attorney ASAP to reply to the NOID. Compile more and better evidence of the bona fides of the relationship.
This response is provided for informational purposes. No attorney-client relationship exists unless we have a signed agreement. For more information, please click on my profile to find my phone number and email address.
They intend to deny your application but they are giving you the opportunity to tell them why they shouldn't. This is your moment so seize it and go find yourself a good immigration attorney to respond to the NOID. It may be the last opportunity you have to prevent them from sending you before the judge to remove you.