When people say genocide, this means that people are usually taken from wherever they are come from, and they are expected to die. A huge amount of people are expected to die because of various reasons. For example, the holocaust is one example of this. There were a lot of Jews who died simply because they were Jews. They were treated inhumanely and were left to die.
During the war, people usually fight with each other. Those who get killed sometimes get killed while in battle. They were literally fighting for their life and for the things that they believe in. For genocide, people who were killed felt like they did not have any choice.