Lori is Rick's wife and… that's about it. She doesn't seem to have an identity beyond wife, mother, or mistress. She's a pretty two-dimensional character. The only background we get on her is when she tells Donna about how she met Rick, a monologue that revolves around her saying how "perfect" Rick is. Twice (353, 356). Rick, the perfect husband, is looking for Lori, believing that she went to her parents' in Atlanta. She didn't. She was taken by Shane to the camp. What happened to her parents? She doesn't seem too concerned that they're probably slobbering zombies. If there's a backstory there, we don't know it yet.
Once she and Rick reunite, we learn that Lori slept with Shane, Rick's partner, when she thought Rick was dead. So she isn't the perfect wife, but is it technically adultery if she thought he was dead? Discuss. (Didn't she read The Odyssey?) When Rick returns, and not as a zombie, she breaks it off with Shane completely, telling him, "You've got to stop this" (519). This sends him on a downward spiral. So we see Lori as someone who ultimately does the right thing, even if someone has to get hurt.
So we've covered "wife" and "mistress." Lori's also a mother. She's content taking care of the kids and doing laundry while the menfolk go off hunting. But Rick takes over parenting duties, too, when he declares that seven-year-old Carl will carry a gun. Lori's not happy about that, but she gets overruled. When zombies attack the camp, Lori's a total failure at helping to do anything. She drops her gun without even firing a shot and has to be saved by Carl. Good thing no one listened to what Lori had to say. Back to the laundry room, woman!