Meaning#

Objects supplied by the embedding application. Do not treat userdata as a table or guess its fields and methods. LuaJIT cdata is a separate category.

Example#

LUA
local function describe(value)
  return type(value)
end

What happens: Only describe is declared; it has not been called, so no call result exists yet.

This fragment does not print or write a log message. The values shown are the expected results of the example.

Methods and related calls#

API reference.