What is the meaning of definitive and specified Primordial germ cells?

[TytoAlba95]

I'm stuck in a dev bio paper. The relevant extract is porovided below:

Human germ cell development begins with the specification of PGCs, which is expected to happen at the onset of gastrulation (developmental week 2) in the posterior epiblast of early postimplantation embryos. During gestation (weeks 3–5), the definitive PGCs migrate from the yolk sac wall through the hindgut to the developing gonads, where they then undergo sex-specific differentiation after week 9. Whereas the male germ cells enter mitotic quiescence synchronously and undergo meiosis after puberty, female human germ cells enter meiosis asynchronously over an extended time period.

The source: cell.

 

[BillTre]

In development (early in gastrulation apparently), the germ cells get specified.
This means they have been induced by some combination of environmental signals within the embryo to become germ cells rather than some other developing structure. They stop cell division or only slowly divide and change things concerning control of transcription, such that they develop as germ cells.
(From an evolutionary point of view, this can be considered advantageous because the cells go through fewer cell divisions before making germ cells, and therefore are less likely to suffer genetic changes before making germ cells.)
These cells become defined in this way as germ cells and then, in order to fulfill their germ cell fate migrate to a different area of the body and enter the genital ridge (gonad primordium) where they settle down and undergo further development.

I am guessing they are using definitive in the sense of: they are defined (perhaps in some clearly observable experimental manner) as germ cells by having their fate determined and set (even it is before they get to their definitive location, which makes the interpretation more confusing).

 

[TytoAlba95]

Thank you :)