"Meeting at Night" was originally published as part of Browning's collection Dramatic Romances and Lyrics. It's a prime example of what's called a dramatic monologue, in which a fictional character reveals something about their personality while recounting a narrative of events. In "Meeting at Night," the events concerned relate to a man heading off to meet with his lover under the cover of darkness.
As the speaker recounts the events of that night, he reveals his single-minded determination to be with his lady love. As well as traveling quickly over the "grey sea," he also walks a mile across the beach and traverses the length of three fields before he arrives at a farmhouse, where he finally meets his beloved. This tells us how important the speaker's lover must be to him. He's so deeply in love with her that he's prepared to travel great distances at night in order to be with her.