Although eschatology isn’t found in the Bible, it does refer to a biblical concept: the end of the world, sometimes called the end times. Eschatology, then is the study and theology of the end of the world as we know it.
The primary book in the Bible to addresses this is Revelation, though other books also contain passages or sections that cover this topic. The last half of Daniel is a key example. The gospels of Matthew, Mark, and Luke all contain an end time teaching as well (Matthew 21, Mark 13, and Luke 21).
Some people read the book of Revelation as a literal account of what will actually happen at the end of the world. Others understand it from a figurative perspective: a great supernatural battle will occur, evil will be defeated, and those who follow Jesus will join him in a new existence (that is, heaven).