Pope wrote "Windsor Forest," from which the above lines are taken, to celebrate the new international relations between nations that Pope saw developing after the signing of the Treaty of Utrecht in 1713. Actually a series of agreements, the Treaty of Utrecht ended the War of the Spanish Succession and created a new awareness of the importance of a balance of power between nations around the world.
Pope's words are symbolically describing countries with varied geographic formations as different types of vegetation all coexisting in peace. Instead of enduring the conflict of being "crushed and bruised," Pope sees the diversity between the nations as being paradoxically "harmoniously confused," finding "order in variety." Like the natural world, nations can coexist in harmony, though they may be of different varieties. The lines rejoice that, after the years of war in Western Europe, an arrangement had been formed in which "though all things differ, all agree" to live in peace.