what does the number of censors represent? I'm trying to understand the ggsurvplot and I stumble about how to interpret the number of censors, like here:

why is it 0 at the start and max = 2 halfway through and at the end?

That's just a description of the underlying data.
A survival time is right-censored when the last observation is made on an individual at that time and the individual hasn't yet had the event. The plot of "censorings" is just how many individuals had such a right-censored observation at the indicated time, color coded in this case according to male/female. The times with n.censor values of 2 are just times when 2 individuals instead of 1 had right-censored observations.
Those censoring times are also seen in the vertical hashes along the survival curves.
