It is one of the longest and thinnest bones of the body. The other bone in the lower leg is the tibia.
The fibula does not carry weight. It articulates (comes together to form a joint) with the tibia above and with the tibia and the talus bone below.
The fibula was compared to a clasp attaching it to the tibia to form a brooch. The fibula is also called the "calf bone".