Others have answered already but I thought it might be useful to add the ? answer:
help?> ...
search: ...
...
The "splat" operator, ..., represents a sequence of arguments. ... can be used in function definitions, to indicate
that the function accepts an arbitrary number of arguments. ... can also be used to apply a function to a sequence
of arguments.
Examples
≡≡≡≡≡≡≡≡≡≡
julia> add(xs...) = reduce(+, xs)
add (generic function with 1 method)
julia> add(1, 2, 3, 4, 5)
15
julia> add([1, 2, 3]...)
6
julia> add(7, 1:100..., 1000:1100...)
111107
So whenever you don’t know what a certain operator/symbol/whatever does, you can try the built-in ? functionality.