QSAR stands for "quantitative structure-activity relationships". It's a way of predicting how powerful and useful a particular chemical will be, based on the structure of the chemical itself. To do this, scientists look at the individual atoms that make up the chemical and how they interact with each other. By looking at how the atoms are connected, we can predict how the chemical will behave in different situations. QSAR can help us understand more about how chemicals work and can help us choose the best chemicals for different applications.