Is https://plugins.gradle.org/m2/ jcenter?

If I use this in my build.gradle does this hit jcenter or something else?

maven {
url “https://plugins.gradle.org/m2/
}

Also, what is different from using gradlePluginPortal() and https://plugins.gradle.org/m2/?

Very little, gradlePluginPortal() creates a maven repo with the default URL https://plugins.gradle.org/m2 (unless the system property org.gradle.internal.plugins.portal.url.override is set).

And no, it is not JCenter.
It is the Gradle Plugin Portal.
But for dependencies it does not host itself, it redirects to JCenter which in turn forwards to MavenCentral for dependencies it does not host itself.