Non-Indian cooks trying Indian recipes for the first time will see “curry leaves” in lists of ingredients.
This is what they look like.
The stem isn’t edible, but the leaves are. I love the flavor. It is very much its own thing, not like anything else.
Curry leaves are available in the refrigerated sections of Indian groceries and are best kept in the refrigerator, but can be stored in the freezer if you aren’t going to use them up fairly quickly.
If they have had time to turn brown, just trash them. In my experience, there is not enough flavor to do any good if they have dried out.