What you said you'd do. All of it.
In any given week you make twenty to thirty verbal commitments. "I'll get back to you on that." "Let me check and follow up." "I'll send you the doc." Most of them you forget within an hour. Some of them the other person remembers for a year.
Follow-Ups captures each one. Yours and theirs. With the audio receipt of who said what and when.
The kinds of commitments Follow-Ups catches
"I'll send you the deck by EOD." — caught, listed, surfaced when it didn't happen.
"Let me think about the offer and get back to you by Thursday." — tracked, with the deadline.
"We need to revisit the timeline after Q1 closes." — calendared as a forward-looking commitment.
"I owe you a thoughtful response to that question." — flagged so you don't skip it.
Their commitments: "I'll have an answer by Friday." — tracked so you can reference it without sounding petty.