A period is used to end sentences, just like in Russian, and to designate file extensions. The following rules refer to English and are really noteworthy.
A period is used with some abbreviations, and always with those abbreviations that would look like a word otherwise.
When a colon introduces a bulleted list, use a period after each entry if it is a complete sentence or a phrase that completes the introduction.
Do not end the entries with periods if they are all short phrases (three words or fewer).
Mr. vs. Mr
British people usually write abbreviations without full stops in modern English.
Full stops are normal in American English.