A keyword is the word or phrase a person types into a search engine, and in marketing it refers to the specific search terms a business chooses to optimise its pages and ads around in order to be found by the right people.
Keywords are how you decide who finds you. Choosing the right ones aims your whole marketing effort at people who want what you sell, instead of broad traffic that never converts.
Search volume is not the goal. A high-volume keyword you cannot rank for, or that brings browsers rather than buyers, is worth less than a lower-volume keyword with clear buying intent.
For a small business, the best keywords are usually specific. Generic terms are fought over by everyone, while specific service-and-location phrases are winnable and bring people ready to act.
A dentist could target dentist, a huge keyword with enormous competition and very mixed intent.
Or they could target emergency dentist in the suburb name, a smaller keyword, but every person searching it is in pain, nearby, and about to book someone.
The specific keyword brings fewer searches but far more actual patients, and it is realistically winnable for a single practice, which the generic one is not.
In-House researches and prioritises keywords through the SEO agent, weighing volume against intent and how winnable each one is for your specific business.