Keyword : Keyword is a set of words or user searched query that is related to a business of related categories.
For example : If someone owns a website that sells mobile phones, then keywords could be anything related to mobile phones like – buy mobile phones online, online mobile phones, etc.
Keyword Prominence : Keyword Prominence is a term that is mentioned in Google guidelines, which means to use keywords in such a way so that a search engine crawlers or robots can easily find it and index a webpage or website against those keywords.
The best for any website to make their keywords search engine friendly and searchable is to put those keywords in meta tags (Meta Title, Description, Keywords).
For example : If someone wants to make their website visible on search engine for some particular keywords then, to put those keywords in title and description is the most reliable way.
Keywords Proximity : Keyword Proximity basically defines the nearness between keywords that are to be used in website.
There are two forms of keyword that can be used in a website, one in main keywords and other is their variants. We know that Search Engines especially Google works on the principle of “similar to” search phenomena, so there is no problem to use variants (synonyms and other similar words) of main keywords.
But Keyword Proximity defines that, to use similar words in a way that best describes that keyword, and you can find a way to use those keywords is to see the pattern of search engine towards those similar words.
Keyword density : is the percentage of keywords in a given content, it generally describes how frequently keywords is used in a content. Commonly, Google says it’s best practice to use a number of 3% keyword density.
For example, if you have a content of say 300 words, then you should use around 9 keyword. This is not mandatory to use such condition, but if you use it describes that you are following the search engine guidelines very well.
Keyword Redundancy : Keyword redundancy is the repetition of same keywords in a content. It basically defines the way of doing non genuine activities, it is same you can say as Keyword Stuffing, which a negative SEO technique.
The above terms describes, the best practice of using keywords in a website so that end user as well as web crawler can easily find the relevancy of keywords to the website.