The words et al. are often used when citing references in text. An example: Smith et al. (2011) reported results from a survey of 90 residents.
The phrase is an abbreviation of the Latin words et alii or alia. Et means “and” and alii or alia means “others”. So the phrase Smith et al. means Smith and other authors and is a way of referring to additional, un-named authors of a reference.
There is no need for a full stop after et because it is not an abbreviation. Only use a full stop after al. Sometimes the words et al. are written in italics because they are Latin words, but this is becoming less common.
The words et al. should never be used in a list of references. The names of all authors of a reference should be provided in the reference list.