Keywords are one of the main parts of any SEO campaign, with the right keywords making the job much easier. Keywords can be made up of different types of phrases:
short tail phrases: these are single words for example, “SEO” or “SEO Packages”
long tail phrases: these are generally several words, perhaps a question, for example “how much is SEO”
Semantic phrases: now we use things like voice search through mobile devices, Google is gradually adding more emphasis to semantic search. This basically means search which uses natural phrases which could be spoken. This is where your question related phrases come into their own.