I've been using IntelliJ IDEA Community 2018.1 for a few months now, strictly with Java and Groovy projects. I just went to import my first (ever) Scala/Gradle project, and when it loaded, I noticed that the IDE wasn't really "loading" the Scala sources (compiling them, etc.). If I opened a Scala source file, it just appeared in the "text editor mode" and if I wrote a line of code that was a flagrant compiler error, IntelliJ didn't complain at all. I also noticed that if I went to create a New File, it didn't give me "Scala" as an option.
So I went into Preferences >> Plugins and installed the Scala plugin, and that made everything work perfectly fine.
However, I then noticed IntelliJ prompting me to configure the "Scala SDK", which I did, and everything is still working as it was when I had only installed the "Scala plugin".
So I ask: What is the difference between the IntelliJ Scala "plugin" and configuring the Scala "SDK"?