Some translations set poetry farther to the right than the rest of the text to show that it is poetry. The ULB does this with the poetry in verses 2-8, 10, 16-17, and 19-24.
The angel prophesies about Babylon falling, which here means being destroyed. It is spoken of as having already happened. This is common in prophecy. It emphasizes that the coming judgment will certainly happen. The angel also prophesies that the people will lament over Babylon falling. (See: [[rc://en/tw/dict/bible/kt/prophet]] and [[rc://en/tw/dict/bible/kt/judge]] and [[rc://en/ta/man/jit/writing-apocalypticwriting]])
Prophecy frequently uses metaphors. This chapter has an apocalyptic style that is slightly different from that of the rest of the Book of Revelation. (See: [[rc://en/ta/man/jit/figs-metaphor]])