It arranges your search volume by separating the relevant keywords from those considered irrelevant. It presents those keywords, which it believes would help rank your search engine very high. Once you indicate that you want your keywords to be filtered, the tool would help to arrange that. You know that is very important for your Adsense and adwords campaign. The program is relevant for your CPC and other internet marketing strategies that you want to use.
If you're a regular blogger, these are probably the topics you blog about most frequently. Or perhaps they're the topics that come up the most in sales conversations. Put yourself in the shoes of your buyer personas -- what types of topics would your target audience search that you'd want your business to get found for? If you were a company like HubSpot, for example -- selling marketing software (which happens to have some awesome SEO tools ... but I digress ;-) -- you might have general topic buckets like "inbound marketing," "blogging," "email marketing," "lead generation," "SEO," "social media," "marketing analytics," and "marketing automation."
The limit on manual keywords could be higher. I personally wish we could input 10,000 keywords at a time, instead of 200. However, I understand the costs that Long Tail Pro has to maintain each time a new manual keyword is input. Not a deal breaker, I just wish the limit was higher. (To be fair, I don't think most keyword tools have a bulk manual option at all).