What's the difference between plane tickets, cashier's checks and electronic tickets?

There is no difference. In fact, electronic ticket is the electronic form of ordinary paper ticket. It realizes paperless booking and boarding procedures by storing passenger information in the computer. In the past, there was no uniform reimbursement voucher for e-tickets, and passengers always used the payment vouchers and boarding passes made by airlines as reimbursement vouchers. Since June 2008, when purchasing e-tickets, passengers can get a "reimbursement form" under the unified supervision of State Taxation Administration of The People's Republic of China, People's Republic of China (PRC) (that is, air transport e-tickets travel to travel itinerary).