Etc. is abbreviation for the latin expression et cetera (or et coetera), which means "and the rest"; "and other things" (of the same species); "and so on". In Latin, et corresponds to the conjunction "and" and cetera corresponds to "the rest".
The abbreviation "etc." is used when enumerating a series of items. The "e" in the abbreviation indicates that other items may be included in the list. Therefore, it is unnecessary to use the conjunction "and" before "etc.".
As it is an abbreviation, it must be accompanied by a dot placed just to the right. When the abbreviation appears at the end of a period, this point will have the function of the final point, it is not necessary to place another indicative point.
Some doubts arise when using the comma before the abbreviation. Some authors argue that, as it is also an enumerative item, the comma must be placed before "etc.". Others argue that the conjunction "and" present in the abbreviation rejects the use of the comma.
However, there is a greater tendency for writers and grammarians to use the comma (or other corresponding period) before enumeration. For example:
"Apples, bananas, grapes, oranges, etc."
The ellipses have the same function as the abbreviation "etc.", and their use together is redundant. The example above could be written as follows:
"Apples, bananas, grapes, oranges..."