The title "Soliloquy of the Spanish Cloister" tells us a few things about the poem we're about to read: first, it takes place in a Spanish cloister, which is the central garden of a monastery. So we know that the poem will be about members of a religious order of some kind, and since we know it's in Spain, we suspect that these monks will be Catholic.
The second thing we learn is that the poem is in the form of a soliloquy, which is a speech or unspoken reflection by a single person (same root as "solo"). So even though the speaker occasionally imagines dialogue with Brother Lawrence, the entire poem is spoken by just one unnamed monk.