Help with R function

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Hi, I have a question with understanding this R script. I don't understand why sapply() has to contain function(x). What happens to the 'x'? This function works if I replace function(x) with function(t) or any other variable. I'm a beginner in R and I would appreciate any help given. Thanks.

simulate <- function(x){
  throws <- x
  sapply(1:2,function(x)sample(1:6,throws,replace=TRUE))
}