A wrapper is any kind of loose cover that encloses something that's for sale. The brightly colored paper that covers your candy bar is a wrapper.
If you wrap something in foil or plastic to sell it, you've made a wrapper. Many wrappers are factory-made and sealed, like the wrapper on your ice cream bar, while others protect your fast-food burger or deli sandwich. In some places, people call a dressing gown or robe a wrapper too. No matter how you use the word, a wrapper wraps something. Its earliest use, in the 15th century, was as "a piece of fine cloth used to wrap bread."