Tell if someone is responding to your text if you both have an iphone?

I sent a text to someone and I saw the the three dots that appear when someone is responding (if they have an iphone) but do those dots also appear if they are just reading the text but not responding? Could someone explain all of the reasons why I'd see the dots as if they were responding?

You see the 3 little dots only if the other iphone owner has iOS-5. If not, you won't even get them.

When you send the iMessage you will see the status of "Delivered". This means it got to their phone, but they haven't read it. When it says "Read" that means they read it.

If you see the dots, and you never get a reply, that means they read it and touched the keyboard but they changed their mind and did not send the reply they were in the process of typing when you saw the dots.