Why is ages just plural you asked.
Many don't know about the ages because it's so often translated as eternal, never world forever more.
There are at least five ages spoken of in scripture and even time before the ages or eons were ever created.
Below you'll see some references for the past ages, the present evil age we are living in, and the next two ages coming.
Here is a definition of a aion which means age
a space of time, an age
◄ 165. aión ►
aión: a space of time, an age
Original Word: αἰών, ῶνος, ὁ
Part of Speech: Noun, Masculine
Phonetic Spelling: (ahee-ohn')
Definition: a space of time, an age
Usage: an age, a cycle (of time), especially of the present age as contrasted with the future age, and of one of a series of ages stretching to infinity
1: before ages
But we speak in a mystery, the wisdom of God having been hidden, which God foreordained before the ages for our glory, 2:7<
As well as these.
Titus 1:2........., 2 Timothy 2:1-9
Here are a few other verses that talk about the age is yet to
And Jesus answering said to them, “The sons of this age marry and are given in marriage, 35but those accounted worthy to obtain that age, and the resurrection that is out of the dead, neither marry, nor are they given in marriage; 36for neither are they able to die anymore—for they are like messengers—and they are sons of God, being sons of the resurrection. Luke 20:34<
and having tasted the goodness of God's word and the power of the coming age.
We are now living in the present evil age.
who gave Himself for our sins, that He might deliver us out of the present evil age, according to the will of our God and Father, Galatians 1:4<
and did make us kings and priests to his God and Father, to him is the glory and the power to the ages of the ages!
There are two ages to come that we know about… Here is one of them:
Anyone who speaks a word against the Son of Man will be forgiven, but anyone who speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.
This talks about two more ages:
To Him be the glory to the Ages of the Ages! Amen. Galatians 1:5<
An age has an end:
As the weeds are collected and burned in the fire, so will it be at the end of the age. Mathew 13:40<
The ages have a purpose:
according to a purpose of the ages, which He made in Christ Jesus our Lord, Eph. 1:10-11<
There has been a mystery hidden from the past
the mystery that was hidden for ages and generations but is now revealed to His saints. Col. 1:26<
There is a king of all the ages:
And to the King of the ages, the incorruptible, invisible, only wise God, [is] honor and glory through the ages of the ages! Amen.<
The ages or were made through the son.
in these last days speaks to us in [His] Son, whom He appointed heir of all things, through whom He also made the ages; Hebrew 1:2<
God promised something before the ages were ever made. Titus 1:2
Talking about a time before the ages were in existence.
upon hope of life age-during, which God, who doth not lie, did promise before times of ages, 2 Tim. 1:9<
to the only wise God our Saviour, is glory and greatness, power and authority, both now and to all the ages! Amen. Jude 1:25<
and He who is living, and I became dead, and behold, I am living through the ages of the ages. Amen! And I have the keys of Hades and of death.
He will be reigning In the next age of ages.
And the seventh messenger sounded the trumpet, and there came great voices in Heaven, saying, “The kingdoms of the world became [those] of our Lord and of His Christ, and He will reign through the ages of the ages!”
Even the smoke goes up untill The ages of ages
And the smoke of their torment goes up until the Ages of the Ages; Rev. 11:11<
His servants will also reign with him through the ages of the ages.
3and there will no longer be any curse, and the throne of God and of the Lamb will be in it, and His servants will serve Him, 4and they will see His face, and His Name [is] on their foreheads, 5and there will be no night there, and they have no need of [the] light of a lamp and of [the] light of [the] sun, because the LORD God gives them light, and they will reign through the ages of the ages.Rev:22 3-5<
To answer your second question: What do these ages stand for?
These ages stand for the coming reign of Christ in the heavens and on the earth.