A Little Free Library is a free book-sharing box where anyone may take a book or share a book. They function on the honor system. You do not need to share a book in order to take one. If you take a book or two from a little library, try to bring some to share to that same library, or another in your area, when you can.
Registered little libraries have a primary caretaker, called a Little Free Library steward. The steward is usually the person who put up the library. The steward takes care of basic maintenance like keeping the library clean and inviting, but it is up to everyone who uses the library to keep it stocked with good books.