Android (Studio) | How is version name defined in Android?

Question

build.gradle

def readVersion() {
    Properties version = new Properties()
    File propFile = file("version.properties")
    FileInputStream stream
    try {
        if (propFile.canRead()) {
            stream = new FileInputStream(propFile)
            version.load(stream)
        }
    } catch (Exception ex) {
        FirebaseCrashlytics.getInstance().recordException(ex)
        println ex
    }
    finally {
        if (stream != null) stream.close()
    }
    if (!version['major']) version['major'] = "1"
    if (!version['minor']) version['minor'] = "0"
    return version
}

def readVersionName() {
    def version = readVersion()
    return "${version['major']}.${version['minor']}"
}

static def readVersionCode() {
    def cmd = "git rev-list --count HEAD"
    return cmd.execute().text as int
}

I can determine the version code and version name in the app via

   String versionCode = String.valueOf(BuildConfig.VERSION_CODE);
   String versionName = String.valueOf(BuildConfig.VERSION_NAME);

Version code is determined by querying "git rev-list --count HEAD", that makes sense to me.

So far so good. But how is version name determined? With my app I get the version name 1.1 But how does that happen? When will it be 2.1 or 1.2 etc. Can I influence that?

Does it have to do with this piece of code of gradle. Why then there is 1 and 0, but in the end 1.1 comes out, I don't get it at all. An what about version.properties, where is that located and what is it for?

if (!version['major']) version['major'] = "1"
if (!version['minor']) version['minor'] = "0"

I've made so many changes to my project, only the version code changes.