Check your card agreement or statement — issuers must disclose it. Common formulas are "2% of balance, minimum $25" or similar, but exact percentages and floors vary by issuer and country, which is why this calculator lets you enter your own numbers.
Because the minimum payment is a percentage of a shrinking balance, the required monthly payment amount also shrinks over time — so you're paying less and less each month while interest keeps compounding on what's left.
For interest cost and payoff speed, yes. The only reason to pay just the minimum is cash flow — if you truly cannot afford more, paying the minimum avoids late fees and credit damage. But it should be a short-term necessity, not a plan.