A cocoon is a covering made of silk thread that some insects, like caterpillars, spin around themselves before changing into their adult form, such as a moth. Inside the cocoon, the insect is protected while its body completely changes. People also use "cocoon" for a safe, comfortable place where a person is protected from the outside world - like being "wrapped in a cocoon of blankets", or someone who "lived in a cocoon", never facing the real world.