These objects contain information about all function calls currently being executed. SE_STACK_INFO(0) represents info on the wrapper function you are in, SE_STACK_INFO(1) is the function that called you, and so forth. The maximum depth you can look back is determined by the compile-time constant SE_MAX_STACK_INFO_DEPTH which defaults to 64. Thus, by default, you may use SE_STACK_INFO(0) to SE_STACK_INFO(63).
Here are the members of each stack info object and what that information is. These members are all read-only: