Pick Mobile if you think in apps
You picture something on a phone screen, with notifications, subscriptions, and an icon on a home screen. Mobile covers Flutter, RevenueCat subscriptions, and AdMob monetisation, so the app can earn from day one.
Pick Backend if you think in systems
You are drawn to the machinery: databases, APIs, authentication, payments, and the parts that keep working when a thousand people show up at once. Backend is the track that makes you useful to every other builder.
Pick Frontend if you think in interfaces
You care how a product feels. Frontend covers React, Clerk authentication, and AdSense, so you can launch a polished web product on your own.
You are not locked in forever. Most builders end up touching all three. The track only decides where you start.