Isaiah lived in the southern half of Palestine - in Judah - and this message was for the people of that nation.

Vision - A supernatural revelation, message, or insight communicated through images seen only within a person's mind or spirit.  The pictures seen in a vision may illustrate spiritual truths or future events.(Quest Study Bible note p 937.)

V 2.
In days to come
the mountain of the Lord's house
shall be set over all other mountains,
lifted high above the hills.
All the nations shall come streaming to it,
NLT.  In the last days, the Temple of the Lord in Jerusalem will become the most important place on earth.  People from all over the world will go there to worship.

Isaiah prophesied that Jerusalem and its temple would become a focal point of worship for teh whole world. Micah, who was a prophet in Judah at the same time as Isaiah, prophesied the same thing.  The nation had lost the glory it had under Kings David and Solomon and was under threat from neighbouring nations.  The northern kingdom, Israel,  had already been overcome by Assyria.  So this prophesy must have been encouraging for the people of Judah, especially if they heard it as one that might come soon - which it didn't!

In Jesus' time the country was on a 'crossroads' of civilisation and, as part of the Roman empire, people were visiting from all over the known world and some non-Jews were interested in the Jewish God and in worshipping at the temple .  People must have wondered if this was what Isaiah had been talking about.

As Christians, we know that it was in Jerusalem that Jesus was crucified and rose again. We remember his words.'But I, when I am lifted up fro m the earth, will draw all men to myself' (John 12: 32 NIV)

In modern times, three world religions which have grown out of the same roots in Israel, see Jeruslem as an important city connected with God - Christianity, Judaism, and Islam.

We must wonder which 'last days' Isaiah was referring to!  When do they start and when do they finish?

Quest Study Bible p 939.  Some believe the last days refer to a future time of God's judgement (the Day of the Lord) followed by Christ's direct rule from Jerusalem.  Others believe the last days began at the time of Christ and his rule in human hearts and will continue until Christ's second coming.

From the New Testament we understand that Christian believers are the new people of God, under a new covenant made through the cross of Christ. In Romans 11 Paul clearly includes the non-Jewish believers as part of 'Israel' - God's chosen people.  The 'new Jerusalem' is where Christ is worshipped and followed.

the mountain of the Lord's house = Mt. Zion , ie Jerusalem.

Psalm 68: 15 - 16 also talks about a similar idea - that higher mountains than Zion will look at Zion in envy because God is there in a special way.

Vs  3, 4.
and many peoples shall come and say,
'Come, let us climb up onto the mountain of the Lord,
to the house of the God of Jacob,
that he may teach us his ways
and we may walk in his paths.'
For instruction issues from Zion,
and out of Jerusalem comes the word of the Lord;
arbiter among many peoples.
They shall beat their swords into mattocks
and their spears into pruning knives;
nation shall not lift sword against nation
nor ever again be trained for war.
NLT.  Many nations will come and say, "Come, let us go up to the mountain of the Lord, to the Temple of the God of Israel.  There he will teach us his ways, so that we may obey him."  For in those days the Lord's teaching and his word will go out from Jerusalem.
          The Lord will settle international disputes.  All the nations will beat their swords into ploughshares and their spears into pruning hooks.  All wars will stop, and military training will come to an end.

Isaiah's prophesy placed an enormous responsibility upon the people of Judah, as God's chosen people.  They were to welcome people from all over the world to worship God in the temple; they were to teach people to know God and to live according to God's wishes; they were to be international peacemakers, representing God, to bring God's peace to the world.

As the 'new Israel' their responsibilities now fall on today's people of God - the believers and followers of Jesus Christ.

V 5.
O people of Jacob, come
let us walk in the light of the Lord.

An appeal for God's people to walk in the light of the Lord.  We can only be effective as God's representatives in teh world if we continue to have a close relationship with him, built through prayer, study of his word, worship and Christian fellowship and nurture.  these things require time to be set aside in our busy lives