Matthew 25:21 His lord said unto him, Well done, thou good and faithful servant: thou hast been faithful over a few things, I will make thee ruler over many things: enter thou into the joy of thy lord.
The parable is about the reward for faithful service which will be given in the kingdom of God.
When Jesus Christ returns he will raise the faithful to eternal life in the kingdom of God which will be established on the earth.
It will commence with a 1000-year reign over the mortal population of the earth.
The faithful will rule with him.
Revelation 20:6 Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.
There will be a hierarchy of responsibility in the kingdom of God.
The twelve apostles, for example, are to be judges over the twelve tribes of Israel.
Matthew 19:28 And Jesus said unto them, Verily I say unto you, That ye which have followed me, in the regeneration when the Son of man shall sit in the throne of his glory, ye also shall sit upon twelve thrones, judging the twelve tribes of Israel.
Luke 22:29 And I appoint unto you a kingdom, as my Father hath appointed unto me;30 That ye may eat and drink at my table in my kingdom, and sit on thrones judging the twelve tribes of Israel.
Others will receive positions commensurate with their humble, faithful service in this life.
Revelation 2:26 And he that overcometh, and keepeth my works unto the end, to him will I give power over the nations: 27 And he shall rule them with a rod of iron; as the vessels of a potter shall they be broken to shivers: even as I received of my Father.
Matthew 18:1 At the same time came the disciples unto Jesus, saying, Who is the greatest in the kingdom of heaven? 2 And Jesus called a little child unto him, and set him in the midst of them, 3 And said, Verily I say unto you, Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven. 4 Whosoever therefore shall humble himself as this little child, the same is greatest in the kingdom of heaven.
Mark 9:35 And he sat down, and called the twelve, and saith unto them, If any man desire to be first, the same shall be last of all, and servant of all.
Luke 14:11 For whosoever exalteth himself shall be abased; and he that humbleth himself shall be exalted.
Luke 22:24 And there was also a strife among them, which of them should be accounted the greatest. 25 And he said unto them, The kings of the Gentiles exercise lordship over them; and they that exercise authority upon them are called benefactors. 26 But ye shall not be so: but he that is greatest among you, let him be as the younger; and he that is chief, as he that doth serve.
I hope you find this helpful.