The Do Not Adopt attribute will add a flag to the top of the Person Record and allow you to enter additional information that can be reviewed and updated from the Memos tab as needed: 

When attempting to complete an adoption outcome to a person who has been flagged with this attribute, users will be alerted with a pop-up warning message to ask for confirmation before proceeding with the outcome:

Attributes also allow you to filter the main dashboard to quickly identify records and they are also available in reports. Please take a look at this related article for additional information: How do I use attributes on people records?