Vouchers are essentially codes that have a monetary value, which can be redeemed online and at Point of Sale. They can have a variable amount but most are sold with a set amount.
PDF designs can be created for online/telephone voucher purchases, and are configured in Print Layouts. Each Voucher type must have a print layout assigned to it. If at least one voucher is configured, then the option to pay online with a voucher will be available.
Whether or not a voucher requires a name to be entered is controlled by the "require recipient name" checkbox against the voucher.