Where to write error message while using error blade directive?

In the code below, I just want to know, where is "$message" is written or stored?

<label for="title">Post Title</label>

<input id="title" type="text" class="@error('title') is-invalid @enderror">

@error('title')
    <div class="alert alert-danger"></div>
@enderror

via Chebli Mohamed