document schema mapping and provide examples of different names

[tacman]

$index = new Index('blog', [
    'title' => new Field\TextField('title', sortable: true),
    'tags' => new Field\TextField('tags', multiple: true, filterable: true),
    'internalNote' => new Field\TextField('internalNote', searchable: false),
]);

In the above and all the examples I can find on the website, the key and the field name are the same. I assume there's map that ways "when you see this key in the document being indexed, store it as a key of this type".

But I'm not sure which is which.

$index = new Index('imdb', [
    'movie_name' => new Field\TextField('title', sortable: true),
    'Genres' => new Field\TextField('genre', multiple: true, filterable: true),
    'Directory Notes' => new Field\TextField('internalNote', searchable: false),
]);

As some of my data comes from CSV files with first columns that are more labels, I'm curious about how the mapping it done.