After a series of wars that lasted for two thousand years, the First Men and the Children of the Forest had fought each other to a standstill. With the two sides tired of bloodshed, representatives of the two races met on an island in the Gods Eye lake in central Westeros, in what today is known as the Riverlands.
The representatives agreed that all open land, field, shore, hill and mountain would be the domain of the First Men, while the deep forest would remain undisturbed under the domain of the Children. The First Men also agreed not to cut down a weirwood ever again.
In the books
In the A Song of Ice and Fire novels, the Pact also led to the establishment of the Green Men, an order sworn to protect and keep watch over the Isle of Faces. It marked the end of the Dawn Age and the beginning of the Age of Heroes.