Vareniky are Russian boiled dumplings filled with potatoes, cheese, berries or anything you might have on hand. You could of course fill them with meat and call them kreplach. The vareniky pictured above were made by my husband and filled with mashed potatoes with plenty of fried onions, and some had a filling of cottage cheese. He served them topped with sour cream and with a side of arugula.
Pilmeny are meat dumplings that are usually smaller than vareniky and I'm told that the main difference between the two dumplings is that the meat in the pilmeny is raw and cooks together with the dumpling, while with vareniky/kreplach you would brown the meat before stuffing.
Some links to vareniky recipes: