POS tagging - NLTK- Python
Your question confuses the nltk itself with nltk_data. You can't really download just part of the nltk (though you could manually trim it down, carefully, if you need to save space). But I think you're trying to avoid downloading all of the nltk data. As @barny wrote, you can see the IDs of different resources when you open the interactive nltk.download() window. 

To use the treebank pos tagger, you need its pickled training tables (not the treebank corpus); you'll find them in the "Models" tab under the ID maxent_treebank_pos_tagger. (Hence: nltk.download("maxent_treebank_pos_tagger").
The FreqDist class doesn't have or need any trained model. 
Neither does word_tokenize, which takes a sentence as a single string and breaks it up into words. However, you'll probably need the model for sent_tokenize, which breaks up a longer text into sentences. That's handled by the "Punkt" sentence tokenizer, and you can download its model with nltk.download("punkt").

PS. For general-purpose use, I recommend downloading everything in the "book" collection, i.e. nltk.download("book"). It's only a fraction of the total, and it lets you do most things without scrambling every so often to figure out what's missing.
I want to use word_tokenize, pos_tag, FreqDist. I don't want to download all nltk as default. I want to use nltk.download(info_or_id=''). What options I should put in info_or_id to get the POS tagging and its frequency. POS tagging - Penn Treebank POS.