When you click on the word like that it is selected. You can drag the word around at that point. If you select some text and drag it around you'll find that it does the same thing. You'll have to select some bigger text so you can click the middle of it and not change the selection.
The upward pointing arrow in green circle indicates that the message will be send as SMS and not as an iMessage. The name/contact of recipient must be green too.
For iMessage the name/contact would be blue.
Contact shown in blue, registered in iMessage:
Contact shown in green, not-registered in iMessage, will be sent an SMS: