API:Type/void

The void type is returned by a Function, YieldFunction, or Callback, to indicate that the member returns no value.

For example, the FindFirstChild function will return nil when it cannot find the given child:

print(type(Model:FindFirstChild('DoesNotExist')))
nil

However, the ClearAllChildren function returns no value:

print(type(Model:ClearAllChildren()))
bad argument #1 to 'type' (value expected)

As a side-effect of how Lua assigns return values to variables, no value is often mistaken as nil:

local result = Model:ClearAllChildren()
print(type(result))
nil