Search & Browsing History (aka Personalization)
Like all other search engines out there, Amazon creates user-profiles and uses this information to personalize search results. It means that your search history and all pages you subsequently visited give Amazon hints about what you are interested in. This information allows Amazon to customize – to a certain extent – your search results in a way that is most relevant to you.
The results are more or less the same on devices with or without a screen, but there are quite a few device-specific factors such as APL that can heavily influence whether a skill ranks higher or lower.