classification if you need to classify the entire sequence you don't want to bind that decision to one particular word what you want to do is you want to have an extra token and that's this cls token that kind of aggregates information from all of this so layer after layer layer after layer you'll have so if we go here layer after layer we have this one special node and in each step every single other node is able to send information right here to this node and receive information from this node okay so now uh