It is rather well explained in psalm chapter 2
Psa 2:4 He that sitteth in the heavens shall laugh: the Lord shall have them in derision.
Psa 2:5 Then shall he speak unto them in his wrath, and vex them in his sore displeasure.
Psa 2:6 Yet have I set my king upon my holy hill of Zion.
Psa 2:7 I will declare the decree: the LORD hath said unto me, Thou art my Son; this day have I begotten thee.
Psa 2:8 Ask of me, and I shall give thee the heathen for thine inheritance, and the uttermost parts of the earth for thy possession.
Psa 2:9 Thou shalt break them with a rod of iron; thou shalt dash them in pieces like a potter's vessel.
Psa 2:10 Be wise now therefore, O ye kings: be instructed, ye judges of the earth.
Psa 2:11 Serve the LORD with fear, and rejoice with trembling.
Psa 2:12 Kiss the Son, lest he be angry, and ye perish from the way, when his wrath is kindled but a little. Blessed are all they that put their trust in him.
Note verse 8. God gave to Jesus the heathen nations. The nation if Israel belongs to God himself, it is his chosen nation out of all the nations of this world. Now Christ may be Israels Messiah but he is the gentiles king. The church is the bride of Christ as in betrothed to him by covenant. Right up into revelations there is a separation made between the nation of Israel and the bride of Christ.
We currently live in the time of the gentiles or the age of grace but that time ends with the rapture. Once the body of Christ is out of here the age of grace ends and things return back to the old laws for the time of Jacobs troubles. In the heavens the church is found before the throne and Christ and they attribute their salvation to the blood of the lamb and their testomany. In other words grace.
Rev 7:9 After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands;
Rev 7:10 And cried with a loud voice, saying, Salvation to our God which sitteth upon the throne, and unto the Lamb.
Rev 7:11 And all the angels stood round about the throne, and about the elders and the four beasts, and fell before the throne on their faces, and worshipped God,
Rev 7:12 Saying, Amen: Blessing, and glory, and wisdom, and thanksgiving, and honour, and power, and might, be unto our God for ever and ever. Amen.
Rev 7:13 And one of the elders answered, saying unto me, What are these which are arrayed in white robes? and whence came they?
Rev 7:14 And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb.
Rev 7:15 Therefore are they before the throne of God, and serve him day and night in his temple: and he that sitteth on the throne shall dwell among them.
Rev 7:16 They shall hunger no more, neither thirst any more; neither shall the sun light on them, nor any heat.
Rev 7:17 For the Lamb which is in the midst of the throne shall feed them, and shall lead them unto living fountains of waters: and God shall wipe away all tears from their eyes.
But the nation of Israel is only found much later before the throne of God and they attribute their salvation to works as in the keeping of the law. Note that the church does not sing the song of Moses.
Rev 15:1 And I saw another sign in heaven, great and marvellous, seven angels having the seven last plagues; for in them is filled up the wrath of God.
Rev 15:2 And I saw as it were a sea of glass mingled with fire: and them that had gotten the victory over the beast, and over his image, and over his mark, and over the number of his name, stand on the sea of glass, having the harps of God.
Rev 15:3 And they sing the song of Moses the servant of God, and the song of the Lamb, saying, Great and marvellous are thy works, Lord God Almighty; just and true are thy ways, thou King of saints.
Rev 15:4 Who shall not fear thee, O Lord, and glorify thy name? for thou only art holy: for all nations shall come and worship before thee; for thy judgments are made manifest.
Now this second group was the one that faced the Mark of the beast, they sing the song of Moses because they are Israelites that faced the time of Jacobs troubles, They acknowledge Jesus as the king of the saints.
Yes both groups serve God but the church is taken out of here before the blowing of the trumpets and the Israelites are taken out of here after the blowing of the trumpets but before the bowls of wrath. Christ and his redeemed saints return after the bowls of wrath at the battle of Armageddon to set up the millennial kingdom.
The covenant God made with Israel is also an everlasting covenant but it is with Israel only, no gentile nation was represented at Mount Sinai when God affirmed his covenant with the nation of Israel through Moses, The gentile nations remain under Christ although he shed his blood for the whole earth, both Israel and Gentile. To the Jew he is the Messiah and to the church he is the bridegroom.