Let's start with one EXTREME of the spectrum:
PRETERISM
Full preterism—or hyperpreterism—is the belief that all prophecy in Scripture has already happened. (The word preterism comes from the Latin preter, which means “past.” As in, the prophecy has already been fulfilled in the past.)
The reason for believing that most of these apocalyptic prophecies were fulfilled before the first century was out is that the book of Revelation is bookended with explicit statements that these prophecies “must soon take place” and that the words should not be sealed up precisely because “the time is near.”
The full preterist, by contrast, believes that all these things have already taken place. The resurrection of the living and the dead has already happened, and there is no future physical second coming of Christ, because that too has already happened.
One theologian sums up the full preterist position like this: “The coming of Christ in judgment was fulfilled in the destruction of Jerusalem in AD 70, Satan and Antichrist have [already] been thrown into the lake of fire, the kingdom of God has arrived, the resurrection is understood in spiritual terms, the Great Commission has been fulfilled, all things have been made new (the old heaven and earth have passed away; the new heaven and earth have come), the promised restoration has arrived, and the world now continues as it is ad infinitum.”
Partial preterism says that prophecies in Daniel, Matthew chapter 24, and Revelation (setting aside the last three chapters) have already been fulfilled. They believe that those prophecies played themselves out in the first century AD, specifically in AD 70 when the Romans destroyed the temple in Jerusalem. What we have in Revelation, therefore, isn’t a symbolic picture of things yet to be fulfilled; it’s a symbolic picture of upheavals and conflicts that happened in the first century. To give one concrete example, “the beast” spoken of in Revelation was Emperor Nero.
That said, to the partial preterist, there are still some prophecies that were a long way off in the first century and are still yet to be fulfilled, such as those given in the last three chapters of Revelation: the visible, physical return of Christ in judgment, the final defeat of death and Satan, the resurrection of the living and the dead, and the coming of the new heaven, the new earth, and the new Jerusalem.
For the partial preterist, the prophecies of Revelation are very much in keeping with the pattern of Old Testament prophetic books: there’s a warning of imminent judgment that applies explicitly to the initial audience of the book, but there’s also the promise of an ultimate restoration that is set firmly in the future.
Partial preterism, then, tries to capture something of an “already but not yet” balance. Enjoying the firstfruits of the Spirit while knowing that our bodies are not yet finally redeemed. Thrilled by the countless prophecies fulfilled by Christ’s first coming, but eagerly awaiting the glorious and very visible return of the King.