Nodes in a cladogram represent the common ancestors of the groups that branch off from that point. In other words, each node signifies a point in evolutionary history where a single lineage splits into two or more separate lineages.
The branches leading away from the node represent the evolutionary paths that these lineages took over time. By examining the arrangement of nodes and branches, scientists can infer relationships between different species and understand how they have evolved from shared ancestors.
Overall, nodes are crucial for illustrating the phylogenetic relationships and evolutionary connections between organisms, acting as markers that help us trace back the lineage of various species through time.