What does Gradle Sync do at the beginning on Android studio, it is very slow?

When I start Gradle Sync on Android Studio, it shows only "Gradle: Build model..." for about 6 minutes without showing any logs.

Does anyone know what it does? Does anyone know how to check the log about what Gradle does?

(FYI, Android Studio version 3.6.3, Gradle build tool version 3.5.3)