In the court system, what does this statement mean: spouse invoked marital privilege after oath?

Some states, including Wisconsin, have a marital privilege. An evidentiary privilege prevents the protected communication from being used as evidence in a legal proceeding. In Wisconsin the rule reads, "A person has a privilege to prevent the person's spouse or former spouse from testifying against the person as to any private communication by one to the other made during their marriage." There are, of course, exceptions. These exceptions include where both spouses are parties to the action (e.g. divorce) or where one spouse is being prosecuted for committing a crime against the other spouse.