This method involves charging a certain fee for including a link on a website. Google does try to avoid most of the paid links, although some of them can have a relevant exposure.
Search engines can penalize or permanently ban you from ranking in the results, due to spammy actions.
Hypertext Preprocessor is basically an open source server scripting language, which is mainly used to render web pages or including any interactive elements to it.
Poison words are words that are known to decrease your pages’ rankings if the search engine finds them in the title, description or URL.
This way the search engine can show a relevant list of results for one search query. For instance, if 10 of the 50 results actually match the search query, the precision would be around 30%.
Many SEO service agencies use this term, which promises top ten rankings with unique methods.