When producing with transfer technology you load a preformed rubber part in a slot and then the machine press a plunge into that slot. In the bottom of the slot you have holes into the cavity. so the material is pressed through the hole and the part is produced.
Saves some times compared to compression. Both in curing time and that you can preform bigger rubber details per cavity.
Disadvantage compared to injection moulding is that you need to produce the preformed rubber parts.
The mould is a little bit more expensive compared to compression moulds.