don't learn it, it's very informal and most people seldom use it.But it's truly means 'is'.不要用它尽量，它不是一个常规用法，是一些人为了装可爱而用的语调，很不正式，也很容易让人笑，不过是你说的意思，就是是的意思

這是個合聲詞 你是念哪個學校 "的啊" ? 他例: 了+ 啊 = 啦 你的理解很接近了!

It doesn't has any meaning. just a mood particle. :)

跟美女聊天了么

yes! its kinda a slang word,very colloquial