What is a round by round poker tournament?

If you are referring to the term "A round" in Poker the answer is the following:

A round is the term for a certain number of hands. Lets say there are 6 players on the table and the button (Dealer) is at player A's location. The button then moves with each hand to the next player (From player A to player B etc). Once the button reaches player A again, the round is finished and a new one starts.