Roll axis rate controller input frequency

Hi, I’ve been away for a while and noted that there are some changes for PID tuning. I try to understand what ATC_RAT_RLL_FILT (and the similar ones for pitch and yaw) is doing.
I had some terrible wobble and played around with the parameters, also toying with the filter frequency in the process.
I couldn’t find any explanation other than the full parameter list description “Roll axis rate controller input frequency in Hz”, which doesn’t really explain how this works and why it was put there in 3.4

Appreciate any comments or pointers if I did indeed overlook them.

Filex

I would like to know this too.