Dot: this mark can be used for different contexts, for example, a mark used in orthography, as above an i. Period: this one is just about grammar and is used at the end of a sentence or paragraph . the first one is just a mark, the second one is a grammatical mark. Hope I clarified your doubt, if you need more ESL grammar lessons I will be more than happy to help you, have a nice day! :)

A period or full stop is the stop used at the end of a sentence. "dot" is a very general word for things similar to the little character used. www dot google dot com I doubt anyone says www period google period com unless describing how to draw the actual character to use. .

think too of morse code 'dot dash dot' - 'period' is in fact not used so much in common speech. If you say 'full-stop' and discard 'period' the question dissolves.