One of the most common ways God uses to communicate his will to humans is through visions. They are vivid apparitions that are distinct from dreams. Although they usually appear during waking (conscious) hours, Scripture does seem to indicate that a person can experience visions while dreaming.
Visions may involve natural or supernatural settings, and the individual experiencing this miracle may be either an observer or a participant. In the Old Testament, they were considered so important that their absence was a cause of great concern (1Samuel 3:1, Proverbs 29:18). Some of the great men of God's word experienced them, often changing their lives and those of others in a dramatic way.
The English word "visions" and its singular form occurs 86 times in the Old Testament of the King James translation and 17 times in the New Testament. In comparison, the words 'dreams' or 'dream' occurs 87 times in the Old Testament and 8 times in the New. The book with the most occurrences of the word (or its singular) is the book of Daniel (32 times) followed by Ezekiel (18).
Who experienced them?
Those who experienced this phenomena as a means of God revealing information to them include Eliphaz (a friend of Job, Job 4), Abraham (Genesis 15), Jacob (Genesis 46), the false prophet Balaam (Numbers 24), Micaiah (1Kings 22) and a very young Samuel the prophet (1Samuel 3). Nathan the prophet was told not only that King David's throne would be established forever but also that David's son (Solomon) would build a temple for God in Jerusalem (2Samuel 7).
Ezekiel had many things revealed to him through visions. The Bible records He was shown God's glory and his throne (Ezekiel 1), was informed of the abominations committed at Jerusalem's temple (chapter 8) and was taken before Israel's elders in Babylonian captivity (chapter 11). He also saw a valley of dry bones representing Israel regathered (chapter 37) and witnessed God at the temple calling for his people to repent (chapter 43).
Daniel saw several visions, including one showing four great world empires (Daniel 7), the Ancient of Days sitting on his throne (Daniel 7:9 - 10) and a prophetic ram and a he-goat (chapter 8). He also saw the events which will occur in the end time (chapter 10).
Isaiah was told, through visions, of future events to occur to the Kingdoms of Judah and Jerusalem (Isaiah 1, 22) and Babylon (chapter 21). Many of the Old Testament's Minor Prophets received this type of revelation, including Obadiah, Nahum, Habakkuk, Amos, and Zechariah.
Peter, James, and John saw the transfiguration of Jesus in a vision and the appearance of Moses and Elijah (Matthew 17:1 - 9). Stephen, just before becoming the first Christian martyr, also was able to miraculously see God's throne with Jesus standing at his right hand (Acts 7:55). A believer named Ananias has Jesus tell him to visit a repentant Saul (Apostle Paul) and heal him (Acts 9).
A Roman Centurion named Cornelius is told to request that Peter come and baptize him just before Peter is miraculously shown a sheet filled with unclean animals (Acts 10). Visions were used to reveal all the events of Revelation to the apostle John.
Apostle Paul's visions
Apostle Paul experiences several miraculous revelations throughout his life. His first one is seeing a man named Ananias coming to baptize and heal him (Acts 9). Soon after his baptism he flees to Arabia, where he is taught the gospel by Christ himself through what is likely a series of visions (Galatians 1:11 - 12, 17 - 18).
Later in Paul's ministry, he miraculously sees in his mind a man from Macedonia asking him for help (chapter 16), being told to speak boldly in Corinth (chapter 18), and informed to leave Jerusalem immediately (chapter 22). Paul is also blessed to see in his mind's eye the 'third heaven' where God's throne resides (2Corinthians 12).
What is their purpose?
Visions serve a variety of purposes. They can convey what will happen in the future (prophecy) or teach spiritual truth. They can be used to strengthen a believer during a trial, reveal events that would otherwise be unknown or reveal God's majesty. They can confirm punishment for sin, inform someone to do the Eternal's will, or even provide encouragement and hope. Lastly, they can confirm a blessing or promise, or reveal our Father's plan for man.
It is a risky thing for any person to claim that God has given them visions when, in reality, he has not done so. Those in the Bible who lied about receiving messages from the Lord, regardless of the means, were put to death in the Old Testament (Deuteronomy 13:1 - 3, 5, see also Jeremiah 23:16, 27, 32).