What is the Second Coming of Christ?
Scripture speaks of the Second Coming in two ways: the visible, glorious return of Jesus to the earth in the clouds, seen by every eye, and (in Hebrews 9:28) a coming that actually points to the moment a believer receives the Holy Ghost.
The Bible teaches that Jesus will come back visibly and unmistakably. Matthew 24:29-30 says that immediately after the tribulation the sun will be darkened, the moon will not give her light, the stars will fall, and then the sign of the Son of man will appear in heaven, with all the tribes of the earth mourning as they see Him coming in the clouds with power and great glory. Revelation 1:7 confirms this, declaring, Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. This is not a secret event; it is a public, worldwide appearing that even the kings, great men, rich men, chief captains, and every bondman and free man will witness, causing them to hide in the dens and rocks of the mountains and cry out for the mountains and rocks to fall on them and hide them from the wrath of the Lamb, as Revelation 6:14-17 describes.
At the same time, there is another dimension to the phrase second coming that is drawn from Hebrews 9:28: So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation. While this verse has often been taken to mean Christ's future return from heaven to earth on a white horse to set up His kingdom, it is actually teaching something else: it refers to the moment a person receives the Holy Ghost. Jesus died on the cross and paid for sin, and now, for those who seek His Spirit, He returns to them by entering their lives in the form of the Holy Spirit. This is confirmed in Acts 3:19-20, which says that when people repent and are converted, so that their sins may be blotted out, times of refreshing come from the presence of the Lord, and He sends Jesus Christ to them.
So the Second Coming, understood broadly, includes both the personal, spiritual coming of Christ by His Spirit into the life of every believer who repents and receives Him, and the future, visible, glorious coming of Christ to the whole earth, when every eye will see Him and the wicked will tremble before His wrath.
The scriptures
Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken: And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen.
And the heaven departed as a scroll when it is rolled together; and every mountain and island were moved out of their places. And the kings of the earth, and the great men, and the rich men, and the chief captains, and the mighty men, and every bondman, and every free man, hid themselves in the dens and in the rocks of the mountains; And said to the mountains and rocks, Fall on us, and hide us from the face of him that sitteth on the throne, and from the wrath of the Lamb: For the great day of his wrath is come; and who shall be able to stand?
So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.
Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord; And he shall send Jesus Christ, which before was preached unto you:
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.