With regard to quotation marks adjacent to periods and commas, there are two styles of punctuation in widespread use. While these two styles are most commonly referred to as “American” and “British” respectively (and some style sheets provide no other name), some American writers and organizations use the “British” style and vice versa. Both systems have the same rules regarding question marks, exclamation points, colons and semicolons. They differ on the treatment of periods and commas.
In the U.S., the standard style is called American style, typesetters’ rules, printers’ rules, typographical usage, or traditional punctuation, whereby commas and periods are almost always placed inside closing quotation marks. This style of punctuation is common in the U.S., Canada, and in the U.K. in fiction and journalism.
The other standard style—called British style or logical punctuation—is to include within quotation marks only those punctuation marks that appeared in the quoted material, but otherwise to place punctuation outside the closing quotation marks. According to The Chicago Manual of Style, this system requires extreme authorial precision and occasional decisions by editors.