A false confession is when a person who did not actually commit a crime admits guilt for committing the crime.
False confessions can be a major problem for the legal system because they can result in the wrong person being held accountable for a crime while the person who is actually guilty remains unaccountable.
There are many reasons why a person may make a false confession. For example, they may be intimidated by a police interrogation, they may be trying to prevent a loved one from being held accountable, they may not be mentally sound and therefore don't understand the consequences of what they are doing, etc.