I just recieved my first bottle of Rodinal. Now, I know on this forum are many advices for different films/Rodinal combinations, so I won't ask what dilution for which film. Something else I would like to know.

I saw different people use different dilutions for same film. For example different people who use for example FP4 some use 1:25, others use 1:50, others use 1:100 dilution, etc...

My question is what different dillutions do, that is what is difference between 1:25, 1:50, 1:100, that is why people use different dilutions for same film?

Oh, by the way, Rodinal is one shot developer , right?

Thank you.