What is keyword difficulty in ASO?

Keyword difficulty estimates how hard it would be for your app to rank well for a given search term, judged from the evidence available: how strong the currently-ranking apps are, and how many reviews guard the top positions.

Every app wants to rank highly for "photo editor", but almost no new app can have it. The winnable game is finding terms where the intent is good and the incumbents are beatable. Kickstart gives every keyword both a difficulty rating and an entry barrier rating, because reaching the top ten is the first useful foothold – and both are scored from live results rather than from search volume figures Apple doesn't publish.