Central to MLA Style, 8th edition, is the concept of core elements and containers. Core elements such as author, title, version, and publishing information are details that apply to all types of sources, regardless of format. They are put together in a specific order and with specific rules for punctuation and capitalization.
Containers are used when a source lies within another source. For example, a book could be cited as a whole and stand alone without a container. But if you are only citing one chapter within a whole book, the book becomes the "container" in which the chapter is found. Articles are part of a whole journal (the container) and an online journal may be found within a database (a secondary container) of journals.
MLA has created a downloadable Practice Template to guide writers in building correct Works Cited list citations.
The images below are copied from the online MLA Style Center and illustrate the concepts of core elements and containers. Note that the correct punctuation appears at the end of each core element.