Can I send and receive iMessage on Mac without buying an iPhone? I have an Apple ID.

Macbook Air has iMessage installed.

But I cannot figure why I cannot send and receive iMessage to friends.
I can only receive messages from myself.

Can you explain how iMessage will work on Mac?

Thanks.
I will answer my question myself.

This is easy to have a try. You can send an receive iMessage when you are online. To send a message, you only need to set the receiving address an Apple ID, or some phone numbers related to the ID. Of course, you network must be well enough to connect to apple.