I might be wrong but I think this is how roblox formats the function Create.
Imagining Tween Service as a class and Create as its method here -
function TweenService:Create(object,info,goals)
for key,value in pairs(goals) do
object[key] = value
end
end
That parameter goals, expects a dictionary from which it sets the key of the object to the provided value.
again there is no possible way for me to know how they format this but from a basic understanding this can be done.