the parting line is the plane at which the two halves of the die meet. The designer must think through each part carefully, as much of the die cast success (or not) will depend on the construction of parting surfaces. The parting line should be kept as straight or flat as possible in general.
The ejector pins are the steel bars used to remove the casting component from the tooling. Good tooling maker will reduce the “visible” marks to minimum. Designer may advise on the appropriate locations of the ejector pins.