There has been much discussion about what is meant by the first resurrection from Rev 20:5.
Perhaps Jn 5:25-29 has some clues as to what the 2 resurrections are.
“Truly, truly, I say to you, an hour is coming, and is now here, when the dead will hear the voice of the Son of God, and those who hear will live. For as the Father has life in himself, so he has granted the Son also to have life in himself. And he has given him authority to execute judgment, because he is the Son of Man. Do not marvel at this, for an hour is coming when all who are in the tombs will hear his voice and come out, those who have done good to the resurrection of life, and those who have done evil to the resurrection of judgment. (Joh 5:25-29, ESV)
In v.25 we see that there is a resurrection that Jesus says “is now here” when the dead hear His voice and live. This seems to be the first resurrection, that of being born again.
In v.28-29 Jesus only says that “a time is coming,” He does not claim that it is now here as the other verse did. This is the resurrection of the just and unjust, which would be the second resurrection – the resurrection of judgement.