This diagram comes from Dr Ralph Lorenz’s book Saturn’s Moon Titan: Owners’ Workshop Manual
It shows -among other things - the hydrological cycle by which methane rises into Titan’s atmosphere and then turns into other chemistry, which falls back to the surface as (I think) rain. I’ve added some annotations as my understanding of it.
Have I got it right?
CHEERZ
DECLAN 
XXX
SCIENCE AGE: 12
Dr Lorenz talks about this stuff in Chapter 7, but it’s a tad over my head