What are app store search suggestions?
Search suggestions are the phrases the App Store and Google Play offer as you type — a public trace of what people actually search, roughly in order of how often.
Neither store publishes search volume, so suggestions are the closest free signal. A phrase that appears as a suggestion is searched; one that never appears rarely is.
Following the suggestions of the suggestions — typing each one and a space — turns a few seed words into hundreds of real search phrases.