Version control, applied to marketing, means maintaining a clear, attributed record of what a campaign, page, or piece of creative looked like at each point in time, and who made each change — the same underlying concept software engineering has relied on for decades, applied to marketing assets instead of code.
Without version control, "what did this look like before the last edit" is often unanswerable, and "who approved the version that’s currently live" depends on someone’s memory. Marketing assets change frequently and are touched by multiple people, which makes this gap more consequential than it might first appear.