A credit card allows cardholders to pay for goods and services with the promise to pay for them later. It provides convenience over other payment methods like debit cards or checks. For merchants, credit cards are more secure than cash and reduce processing costs. There is typically a grace period of 20-55 days before interest is charged on purchases, allowing customers to pay their balance in full each month without interest. Different credit cards have varying interest rates, annual fees, rewards programs, minimum payments, and grace periods. While credit cards provide benefits like rewards, their disadvantages include potential interest charges and fraudulent activity risks.