Rabbits use two types of scent glands to mark their territory and communicate vital stats among one another—one under their chin and the other in their vent area. You may have noticed your bunny rubbing her chin on furniture, toys, food, or even you. It's her way of claiming ownership and proudly declaring, "That's mine!" You can sometimes observe rabbits, as well as various other mammals, scratching their chins with their hind legs and running around their (sometimes invented) territory, distributing their scent around the perimeter.
While the chin scent glands serve as subtler hints, the scent glands in the vent area, called inguinal scent glands, located on either side of the genitalia of both males and females, excrete a strong smell detectable even by humans. The rabbit is able to attach this scent to specific kinds of territorial droppings. However, rabbits frequently do not clean themselves properly, either due to weight or laziness, and the glands can become impacted and require your assistance.
When the inguinal scent glands are noticeably odorous, it’s time for a cleaning. I'll preface this by saying that you can't expect every part of owning a pet to be pleasant and great fun. Inguinal scent gland cleaning likely ranks high up there with the world's less pleasant pet ownership duties, but it's truly not that bad (besides the unpleasant odor). Your veterinarian can show you how to do it the first time, or you can just have them do it at quarterly vet visits. It's possible to do it at home as long as you can get a good grip on your rabbit, or wrap her in a towel, and are able to secure them on their backs or bottoms. If you're really skilled, you can do it by yourself, but the first few times you'll want to ask a (really) good friend to help out.
First, grab some Vaseline, Q-tips and tissues. Make sure you are sitting on the floor, so if the poor thing does wriggle out, she is safely close to the ground. Make the vent area accessible and expose the two slits on either side of the genitals. With a Vaseline coated Q-tip, wipe out the dark brown waxy substance.* Keep in mind to do all this very carefully because the area is very sensitive and be aware that many rabbits get quite offended by all the activity down there, so keep them calm by talking soothingly and petting their heads. That's pretty much all there is to inguinal scent gland cleaning. I hope it's not as terrible as you imagined!
*Hold your breath while doing this.