Meaning: actually, in reality.
Example: Sophie said, “No matter how well you argue Lucy, the fact of the matter is that you never help around with the chores. And neither do you buy your share of groceries. Why should I do your share of the work and pay your bills too?”
Lucy knew that Sophie was right. She needed to be more responsible. She decided to buy the groceries and cook dinner for both of them today. She hoped Sophie would forgive her.