diff --git a/Exit-Code-Mappings.md b/Exit-Code-Mappings.md
index a086487..453ff07 100644
--- a/Exit-Code-Mappings.md
+++ b/Exit-Code-Mappings.md
@@ -58,17 +58,17 @@ Runner: https://github.com/ReCodEx/utils/blob/master/runners/py/runner.py
 | --------- | --------- | ------- |
 | 0 | --- | OK |
 | 1 | BaseException | Unhandled exception |
-| 101 | AssertionError | Assertion error |
-| 102 | TypeError | Type error |
-| 103 | NameError | Name not found error |
-| 104 | EOFError | End of file error |
+| 101 | AssertionError | An assertion failed |
+| 102 | TypeError | Type error (a different type was expected) |
+| 103 | NameError | Name not found error (an undefined name was used) |
+| 104 | EOFError | End of file error (`input()` encountered an EOF) |
 | 105 | AttributeError | Attribute access failed |
 | 106 | IOError | IO error |
-| 107 | OSError | OS error |
-| 108 | LookupError | Lookup error |
-| 109 | ValueError | Value error |
+| 107 | OSError | OS returned an error (including filesystem access errors) |
+| 108 | LookupError | Lookup error (invalid key or index was used in a data structure) |
+| 109 | ValueError | Value error (invalid value of the right type was encountered) |
 | 110 | ZeroDivisionError | Zero division error |
 | 111 | ArithmeticError | Arithmetic error |
-| 112 | ImportError | Import error |
+| 112 | ImportError | Import error (an unknown or forbidden module was imported) |
 | 113 | MemoryError | Memory allocation error |
 | 114 | SyntaxError | Syntax error |