100% test coverage means that every part of the code has been executed and tested by your test suite at least once. This includes:

1. Function Coverage: Every function in the code has been called.
2. Statement Coverage: Every individual statement in the code has been executed.
3. Branch Coverage: Every branch (i.e., both the true and false branches of every condition) has been taken.
4. Condition Coverage: Every condition in the code has been evaluated to both true and false.

However, it’s important to note that 100% test coverage does not necessarily mean that the code is free of bugs. It only indicates that all lines of code have been executed by tests. The quality of the tests, such as whether they check for correct outputs and handle edge cases, is also crucial for ensuring the reliability and robustness of the code.