Use of PunktSentenceTokenizer in NLTK

Question

I am learning Natural Language Processing using NLTK. I came across the code using PunktSentenceTokenizer whose actual use I cannot understand in the given code

Answer 1

def process_content(corpus):

    tokenized = PunktSentenceTokenizer().tokenize(corpus)

    try:
        for sent in tokenized:
            words = nltk.word_tokenize(sent)
            tagged = nltk.pos_tag(words)
            print(tagged)
    except Exception as e:
        print(str(e))

process_content(train_text)

Without even training it on other text data it works the same as it is pre-trained.