Utilize means to use something — but with a particular flavour that plain 'use' does not always have: to make good, practical, or clever use of something, often something that was there all along and might otherwise be wasted. You utilize a skill you already have, waste heat from a factory, empty space under the stairs, the data a company already collected. That is the sense in which the word truly adds something. Honestly though, most of the time people write utilize simply because it sounds more serious than 'use', and in those sentences it adds nothing at all. 'We utilized a hammer' is not better English than 'we used a hammer'; it is worse, because it is heavier for no reason. English style guides have been telling writers this for a century, and it is good advice: if 'use' fits, use 'use'. The word belongs in business reports, scientific papers, official documents and job applications. In conversation it can sound stiff, or even a little pompous, and some listeners will quietly think the speaker is trying to sound clever. Young people say it less than older office-trained speakers do. British writers may spell it 'utilise'; Americans always write 'utilize'. It is a regular verb — utilize, utilized, utilizing — and it takes a direct object: you utilize something.