The first resurrection is Jesus himself insofar as he was resurrected and then became the source of all subsequent resurrection. Believers are then said to be those who “take part in the first resurrection”, and are “not harmed by the second death”.
So to be born again is to be spiritually resurrected and risen with Christ, seated with him and reigning with him on high as kings and priests. New creations, and part of the new creation to be revealed at the end, as well as what that implies for life while here.
The second resurrection is the bodily rising of all people for judgement when Christ returns, although believers are said to be already judged and liberated from death to life. Because “this is the judgement…” (John). Which means THE REST are also “already judged” and are guilty of not receiving freedom from judgement while they had the opportunity to do so. Those who have already taken part in the first resurrection, in Christ, are the subject of what is called the rapture, and are taken up to be with Him when he returns. In common parlance, THE REST are subject to “the great white throne judgement”, which simply means that the appearance of Jesus that saves believers, is the same appearance that brings ‘destruction’ to THE REST, and is called “the second death”.
The second resurrection is the Armageddon end time event of “the just and the unjust”.