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Bottom line, content should be natural for a reader.
Content should be obviously about and aligned with the keyword focuses of the request. Said another way, you should not be able to mistake the focus of the page as anything other than the original keywords requested.
Shoot to use a keyword phrase ”Polaris ATVs” roughly 3-5 times per page. You can use it more often if usage is natural and no obvious alternate phrasing comes to mind. Instead, synonyms or related phrases can be used.
Overusing a keyword is generally called “keyword stuff”. This basically just means that you should not mention keywords so frequently that is becomes unnatural to read. You can also read Google’s official documentation for Keyword Stuffing.
Pages
Meta Description
Internal Linking
Semantic SEO
LSI Keywords