2 1
The Apostles 4 filled with the holy Ghost 8 speak with divers
tongues: 12 They are thought to be drunk, 15 but Peter disproveth
that. 34 He teacheth that Christ is the Messiah: 37 And seeing the
hearers astonied,  38 he exhorteth them to repentance.

1 And [ag]when the day of Pentecost was [ah]come, they were [ai]all with one accord in one place.

"Pentecost" - Pentecost was originally a Jewish festival/celebration.  It just
so happened that the coming of the Holy Spirit fell on the day of
Pentecost, which is to take place 50 days from the second day of
Passover. Christians today still celebrate Pentecost 7 weeks after the
second day of Passover(also 7 weeks after the resurrection). This means
that the celebration of Pentecost always falls on a Sunday, while the
Jewish celebration of Pentecost varies depending on when Passover falls.

"Pentecost, n." OED Online. Oxford University Press, March 2015. Web. 27 March 2015.

2 And suddenly there came a sound from heaven, as of a rushing and mighty wind, and it filled all the house where they sat.

3 And there appeared unto them cloven tongues, like fire, and it sat upon each of them.

"cloven" - divided or split. "Cloven" is used to represent the different tongues that were present/how greatly all of the languages contrasted.

"cloven, adj. and n." OED Online. Oxford University Press, March 2015. Web. 27 March 2015.

4 And they were all filled with the holy Ghost, and began to speak with [aj]other tongues, as the [ak]Spirit gave them utterance.

5 And there were dwelling at Jerusalem Jews, men that feared God, of every nation under heaven.

The Roman empire had expanded to encompass nations ranging from an extremely large geographical area, which is why it makes sense that there were people of so many nations present here. The description of the specific nations that are present beginning in verse 9 is intentional. The first nations mentioned are on the easternmost border of the Roman empire. The empire is then described in a counter-clockwise fashion, listing the northernmost, westernmost, and then southernmost nations.

MacLean, M. "8th June: Pentecost: Acts 2.1-21." The Expository Times. 125.8 (2014): 392-393. Print.

6 Now
when this was noised, the multitude came together and were astonied,
because that every man heard them speak his own language.

7 And they wondered all, and marveled, saying among themselves, Behold, are not all these which speak, of Galilee?

8 [al]How then hear we every man our own language, wherein we were born?

9 Parthians, and Medes, and Elamites, and the inhabitants of Mesopotamia, and of Judea, and of Cappadocia, of Pontus, and Asia,

10 And of Phrygia, and Pamphylia, of Egypt, and of the parts of Libya, which is beside Cyrene, and strangers of Rome, and [am]Jews, and Proselytes,

11 Cretes, and Arabians: we heard them speak in our own tongues the wonderful works of God.

12 [an]They were all then amazed, and doubted, saying one to another, What may this be?

13 And others [ao]mocked, and said, They are full of new wine.

14 ¶ But Peter standing with the eleven, [ap]lifted up his voice, and said unto them, Ye men of Judea, and ye all that inhabit Jerusalem, be this known unto you, and hearken unto my words.

In verse 41, it is said that this event resulted in 3,000 new believers. It is debated whether the new believers are the direct result of the miracle the people had witnessed, or the words of Peter. The most popular opinion is that the words of Peter, combined with the hand of God in the hearts of the listeners, brought about the conversions. This is backed up with the presence of "With many other words" in verse 40. The scripture implies that there are other conversations/arguments that the people have been exposed to that effect their decision to believe in Christ.

 Kilgallen, J J. "Commentationes - 'with Many Other Words' (acts 2,40): Theological Assumptions in Peter's Pentecost Speech." Biblica. 83.1 (2002): 71. Print.

15 For these are not drunken, as ye suppose, since it is but the [aq]third hour of the day.

16 But this is that, which was spoken by the [ar]Prophet Joel,

17 [as]And it shall be in the last days, saith God, I will pour out of my Spirit upon [at]all [au]flesh,
and your sons, and your daughters shall prophesy, and your young men
shall see visions, and your old men shall dream dreams.

18 And on my servants, and on mine handmaids I will pour out of my Spirit in those days, and they shall prophesy.

This is the spirit that the disciples received that caused them to speak in tongues.

19 And I will show wonders in heaven above, and tokens in the earth beneath, blood, and fire, and the vapors of smoke.

20 The Sun shall be turned into darkness, and the moon into blood, before that great and notable day of the Lord come.

21 [av]And it shall be, that whosoever shall [aw]call on the Name of the Lord, shall be saved.

Romans. NIV. N.p.: n.p., 2011. Bible Gateway. Web. 27 Mar. 2015.

22 [ax]Ye men of Israel, hear these words, JESUS of Nazareth, a man [ay]approved
of God among you with great works, and wonders, and signs, which God
did by him in the midst of you, as ye yourselves also know:

23 Him, I say, being delivered by the determinate counsel, and [az]foreknowledge of God, after you had taken, with wicked [ba]hands you have crucified and [bb]slain.

24 [bc]Whom God hath raised up, and loosed the [bd]sorrows of death, because it was impossible that he should be holden of it.