@params['user'].delete('form') - what does .delete('form') do?

Trying to understand the SaltedHashLoginGenerator and came across this.
What does the .delete('form') do?

Thanks!

Trying to understand the SaltedHashLoginGenerator and came across this.
What does the .delete('form') do?

http://corelib.rubyonrails.org/classes/Hash.html#M000710

Deletes and returns a key-value pair from hsh whose key is equal to key. If the key is not found, returns the default value. If the optional code block is given and the key is not found, pass in the key and return the result of block.

    h = { "a" => 100, "b" => 200 }
    h.delete("a") #=> 100
    h.delete("z") #=> nil
    h.delete("z") { |el| "#{el} not found" } #=> "z not found"