Most turf grasses tend to be blends with a couple of distinct exceptions, usually associated with hot and rather dry climates. I would be very surprised if you lawn wasn't a blend of different turf grasses as well. And those blends are extremely hard to differentiate, especially with only a photo.

I'd suggest taking a sample to your local extension service for an accurate ID. And after identification, they will be able to guide you with your care needs - unfortunately, info from Purdue (Indiana) is not going to be very relevant for the southern Atlantic coast :-))
You could also try posting in the Lawn Care forum or your regional forum. Not sure they'd be able to ID exactly for you but can certainly help with regionally appropriate care tips.

Thanks for the reply gardenGal

Your first pic looks like the fescue in my yard, where it doesn't really grow that thick together (still can see patches of ground). But the second picture looks like a pretty nice thick growth.

It is evergreen in my area (not sure if there is a zone it might go dormant in), and it grows well in shade and is heat-tolerant. If it only would grow thicker, I'd very much enjoy it to be my grass of choice in my lawn, but since it grows sparsely, it just looks like a weed in the winter/early spring season and doesn't fill in the lawn all the way in the spring and summer seasons.