Revelation 17 & 18 speaks of the destruction of Babylon the Great, the world empire of false religion. She is described as a harlot because she commits spiritual fornication with the kings and governments of this world. The governments will turn against religion, but Revelation brings out that God will put it in their hearts, so to say. This judgment will come from God due to her shameful acts and lies.
I guess it's about some prostitute who is judged by God and I think a lot of it is symbolism even though it might be literal also... I know this is vague so maybe you could go talk to your pastor about it :)