Keyword Difficulty is a score estimating how hard it is to rank on the first page for a keyword, based on the strength and competition of the apps already ranking for it.
Keyword difficulty (sometimes "keyword competition") helps you decide where to spend effort. A term might have high search volume but be dominated by entrenched apps with massive download velocity and thousands of reviews — ranking there is a long, expensive fight. A lower-difficulty term with decent volume is often the smarter target, especially for a newer app that needs early wins to build the performance signals that unlock harder terms later.
Difficulty is always relative to your app's authority. The same keyword is "easy" for a market leader and "impossible" for a launch-week app. Good keyword research pairs difficulty with volume and relevance: chase the terms where your realistic ranking potential, the traffic on offer, and the fit with your app all line up.
Example
A new note-taking app skips the brutal "notes" keyword (high volume, high difficulty) and targets "voice notes transcription" — lower difficulty, high relevance, winnable in weeks. Re-score your targets as the app gains authority — terms that were unwinnable at launch open up once velocity and ratings build.