Info
comes from the function that starts the child process (as given in the child specification in the supervisor). Most of the time, that function will eventually call gen_server:start_link/4 which only returns {ok, Pid}
and never {ok, Pid, Info}
, so that case only applies when you have a custom function for spawning the process, probably using the functions in the proc_lib module.
Processes that don't use a pre-defined behaviour are called "special processes" and are described in the OTP Design Principles User's Guide.