.Set - Unable to understand the statement

[ateestructural]

I have the following code which I have inherited it from someone else.

vocab_filename = 'vocab.txt'
vocab = load_doc(vocab_filename)
vocab = vocab.split()
vocab = set(vocab)

I know in the steps above: document gets loaded into the memory

(vocab = load_doc(vocab_filename)

, split into words

vocab = vocab.split()

but I do not follow what this last line is actually doing;

vocab = set(vocab)

Can someone help me understand what the above line does?

Thanks a lot, in advance