Scholars tend to conclude that the speaker and the listener (auditor) in the poem are based on Arnold and his wife. It is likely that Arnold wrote the poem on the coast while he and his wife were on their honeymoon. However, there is nothing in the poem that directly points to the young man being Arnold and the woman/auditor being Arnold's wife. So, within the context of the poem, the speaker is any young man and the auditor is the woman he is with.
In the poem, the man/speaker looks out from the coast towards France. He encourages his lover/companion to look with him. He comments on the melancholy sound of the waves and compares it to a similar line in Sophocles' Antigone. The speaker then laments the loss of a religion to unite people. To compensate for that loss, the speaker suggests to his lover (auditor) that they should live for each other:
Ah, love, let us be true
To one another! for the world, which seems
To lie before us like a land of dreams,
So various, so beautiful, so new,
Hath really neither joy, nor love, nor light,
Although the world has nothing to offer ("neither joy, nor love, nor light," no unifying religion, and a world "Where ignorant armies clash by night"), the speaker clings to the idea of love as life's saving grace.