HF term explained
HF (high frequency search keywords) is the most requested word (words, phrases) in your theme (most popular keywords). Usually high frequency queries are the key phrases of one word, like seo or blog. In different subjects the number of queries of certain HF can vary from thousands to several tens and even hundreds of thousands.
Also HF are often highly competitive queries and therefore, they optimized the home page with the maximum Link Weight/Link Juice. Not to be confused with high-frequency and highly competitive queries, because some high-frequency queries can be quite competitive.