Packages are sets of files (usually defined in the same directory) that define logic units, for example, controllers, and repositories.

To set a file in a particular package, use the package keyword in the first line:

package com.packt.functionalkotlin

Ideally, a file inside the package com.packt.functionalkotlin should be in the directory com/packt/functionalkotlin. It makes files easier to find but isn't mandatory in Kotlin.