Text communication with iphone users
SMS works on any phone. On Android, your phone will have an SMS client built-in (probably called "Messaging", but it varies between manufacturers), and you can also choose from many third-party SMS clients.

As well as plain old SMS, there are many instant-messaging systems that work on Android and iPhone, and other platforms too. Your iPhone-using friends may well have one or more of these installed already. Some examples are Skype, Jabber, Whatsapp, Google Hangouts, and Facebook Chat.

What you describe as "apple messaging" is probably what Apple calls iText: it's the SMS app on iPhone. It also has its own closed chat system built-in, so that if it knows the recipient of an SMS is an iPhone, it'll silently send the message through Apple's servers instead of through the SMS system. It still uses SMS for people on other phones, so you don't need to worry about being exiled.