Acts 2:3 NIV
They saw what seemed to be tongues of fire that separated and came to rest on each of them.
This fulfilled the prophecy by John the baptizer in Matthew 3:11
I baptize you with water for repentance, but after me will come One more powerful than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and with fire.
What does fire mean in this context?
The fire is symbolic of the Holy Spirit as John prophecied.
And how is the fire related to the divided tongues?
διαμεριζόμεναι γλῶσσαι ὡσεὶ πυρός
divided tongues as of fire
Verb - Present Participle Middle or Passive - Nominative Feminine Plural
Strong's Greek 1266: To divide up into parts, break up; I distribute. From dia and merizo; to partition thoroughly.
Noun - Nominative Feminine Plural
Strong's Greek 1100: The tongue; by implication, a language.
The divided tongues depict different streams of the fiery tongues coming from the one source, the Holy Spirit.
How should we make sense of the individual words and the full expression as a whole?
Let's see the context:
Act 2:1 When the day of Pentecost came, they were all together in one place. 2Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. 3They saw what seemed to be tongues of fire that separated and came to rest on each of them. 4 All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them.
The scenery is full of sound and light inside a house.
The imagery is that of the distribution of many fiery tongues coming on each of the participants individually. There is also the pun of these fiery tongues turning into actions of speaking in tongues.
It was an epoch-making supernatural event that announced the inauguration of the Holy Spirit working together closely with the believers in the New Testament.