what does a merge collection function returns in laravel code example

Example 1: laravel merge collections

/* 
 * The merge method merges the given array or collection with the original collection.
 * If a string key in the given items matches a string key in the original collection,
 * the given items's value will overwrite the value in the original collection:
 */
$collection = collect(['product_id' => 1, 'price' => 100]);
$merged = $collection->merge(['price' => 200, 'discount' => false]);
$merged->all(); // ['product_id' => 1, 'price' => 200, 'discount' => false]

// If the given items's keys are numeric, the values will be appended to the end of the collection:
$collection = collect(['Desk', 'Chair']);
$merged = $collection->merge(['Bookcase', 'Door']);
$merged->all(); // ['Desk', 'Chair', 'Bookcase', 'Door']

Example 2: merge collections laravel

$collection = collect(['product_id' => 1, 'price' => 100]);

$merged = $collection->merge(['price' => 200, 'discount' => false]);

$merged->all();

// ['product_id' => 1, 'price' => 200, 'discount' => false]