“Et al.” is a scholarly abbreviation of the Latin phrase et alia, which means “and others.” It is commonly used when you don’t want to name all the people or things in a list, and works in roughly the same way as “etc.” “The reorganization plan was designed by Alfred E. Newman, General Halftrack, Zippy the Pinhead, et al.; and it was pretty useless.” The “al.” in this phrase needs a period after it to indicate it is an abbreviation of alia, but it is incorrect to put a period after “et.”