Essentially, (if my high school history had it correct) it's an extreme form of violence designed to force a targeted people to leave the land they are living on. People used to use this term a lot more in older days (back in the 80s), but now we just use the term genocide since pogroms usually are an aspect of genocide - the Armenian Genocide, for instance, had a lot of pogroms going on. They are also a key aspect of settler-colonialism - which is how Palestinians ended up being one of the largest refugee populations in the world.