What does the i symbol next to a delivered text mean?

[sexandthecitylover]

I have my delivery report option turned on on my phone.

In the sent box some of the texts have a little i symbol next to them. I thought this meant delivered but some texts do not have this symbol and yet in the delivery report folder it says they have been delivered.

Does the i symbol meant they have been read for example.

The phone is Nokia.

Just curious.