- The type of device used for the search (desktop, laptop, phone, tablet) Your personal search history
- Whether you are logged in to a Google Account while searching
- Your geographic location
- What type of browser you are using
- The number of Google-generated ads on the page
- What type of search you are doing (intent)
- The time of day you’re searching (results vary based on opening/closing times of your business also)
- And finally, the most important reason: The phase of the moon (ok not really, but with Google you really never know).
Learn more here: http://direction.com/understanding-seo-and-google-algorithms/