Custom machine is a mobile phone with mobile 3 and 4G signals. Because the signal standard of each operator is different and the hardware should be distinguished, there will be mobile custom machine, Unicom custom machine and Telecom custom machine. Contract machines are different. Contract machines are basically from custom machine, but there is another contract based on custom machine. For example, a mobile contract machine will ask you to use a mobile card and how much it will cost each month for several years. Contract machines are generally cheaper, because the operator will earn your mobile phone money back during your contract.