Debug This Error Message With Me

An error message is shouting at you in a language you do not yet speak. Paste the error and the code, and this explains what kind of problem it represents in plain English, points to the exact lines at fault, says why they are wrong, and walks you through the fix step by step. You learn the cause, not just the patch.

I'm getting an error in my {LANGUAGE} code and I don't know how to fix it. Here is the error message:

```
{ERROR_MESSAGE}
```

And here is the relevant code:

```
{CODE_SNIPPET}
```

First, explain what this type of error means in plain English: what category of problem does it represent? Then identify the exact line or lines causing the issue and explain precisely why they are wrong. Walk me through the fix step by step, showing the corrected code. Finally, teach me the debugging habit I should develop to catch this kind of error myself in future: what should I look for first when I see this type of error message?