Sister taxa are groups of organisms that are more closely related to each other than to any other group. In the context of evolutionary biology, sister taxa represent a pair of groups that share a common ancestor more recently than they share that ancestor with other groups.
To understand sister taxa better, imagine a family tree. If you consider two siblings, they are sister taxa in relation to each other. They both descend from the same parents (the common ancestor), and while they may share traits from their parents, they also diverge in various ways due to their own evolutionary paths.
In practical terms, sister taxa can be used to study evolutionary relationships, and they help scientists understand how different species have evolved over time. By looking at the characteristics they share, researchers can deduce information about their common ancestor and further explore the process of evolution.