From HEXONET Wiki
Different types (classes) of domain transfers exist. In order to process a transfer, both the gaining and losing registrar are involved.
PUSH: means that the losing registrar has to initiatate the transfer, basically pushing the domain to the gaining (new) registrar. Some registries require a so-called handshake, meaning that the gaining registrar has to confirm the reception of the domain.
PULL: means that the transfer has to be requested by the gaining registrar. This is the most common transfer-procedure. If a registry allows a realtime-transfer with an authorization code, it will be directly processed without any further steps. Some registries require an additional confirmation by E-mail or FAX.
OTHER: Some registries have their own special procedures to handle a domain transfers. Please contact our Support Team if you should need further information.