Is Android messaging like iMessages?
No. On all Android phones I'm aware of, the "Messaging" or SMS app is just an SMS app. It doesn't try to sucker you into using a proprietary chat service by pretending it's giving you free texts.

There are many IM and chat services for Android if you want to use one instead of texting. Like the iPhone, there's even one that ships with the phone, but unlike the iPhone, it's a separate app, called Hangouts. Hangouts looks and feels like a chat system, not an SMS app, and it includes voice and video calling, sending files, and group calling.

Android allows third-party apps access to all the phone functions, so if you really want to use SMS and a chat system in the same app, I'm sure you can find a third-party SMS app that includes both, such as Skype.