A voucher is a certificate or document that either allows you to purchase something or proves that you paid for something. A voucher is sometimes valuable.
When you can vouch for someone, you're willing to recommend them and say they're a good person. A voucher does something similar. For many workers, a voucher is a receipt that proves they spent money on something, like travel, which their company will later pay for. A voucher is also a type of coupon that allows you to purchase something for less or no money, even tuition to a school. Both types of vouchers allow you to save money.