Botanical Name: Chenopodium album
I have not used lamb's quarters medicinally, but it is a great plant to use as a free food, boosting the nutritional value of anything you add it to. Charmagne, a great volunteer weeder at the You Pick Garden, always "weeds" lamb's quarters out first, putting it in her gathering basket to add to her weekly pesto creation. Thanks to her, I gained an even greater appreciation for lamb's quarter and always leave it for her to use.
Here is a great article thanks to Chestnut Herbs - well worth your time to read it. No need for me to reproduce the information.
Lamb's quarter is very easy to find in our area. If you need any help finding some, let me know. We had lots of it scattered around the You Pick Garden area.