classpath - Purpose of buildscript block in Gradle

Question

I am new to Gradle and I am reading the documentation but I don't understand some parts of it. One of these parts is connected with buildscript block. What is its purpose?

If your build script needs to use external libraries, you can add them to the script's classpath in the build script itself. You do this using the buildscript() method, passing in a closure which declares the build script classpath.

buildscript {
  repositories {
    mavenCentral()
  }
  dependencies {
    classpath group: 'commons-codec', name: 'commons-codec', version: '1.2'
  }
}

Ok but what is the difference with:

repositories {
  mavenCentral()
}
dependencies {
  compile group: 'commons-codec', name: 'commons-codec', version: '1.2'
}

For example, why it is necessary to use buildscript?

Answer 1

The buildScript block determines which plugins, task classes, and other classes are available for use in the rest of the build script. Without a buildScript block, you can use everything that ships with Gradle out-of-the-box. If you additionally want to use third-party plugins, task classes, or other classes (in the build script!), you have to specify the corresponding dependencies in the buildScript block.