Have FB messages been read or really just sent?

If you send normal messages on Facebook (I'm online with a laptop, don't know whether that plays a role) and under the text it says "sent" when you have sent it away, then the recipient has only received it or you can assume that he has has read it too?

Sent does not mean that it has arrived or has been read.

If you are not friends with the person, you will only see when the person answers whether your N. Has arrived and has been read, then you will see the profile picture next to the N., before that it only says sent