Scientists have found that plants releases the chemical with that familiar scent as a way to alert nearby creatures who can rescue them from insect attacks. They studied the wild tobacco plant, and they noticed that they released a compound called Green Leaf Volatiles (GLV).
When the tobacco plants were attacked by caterpillars, they released GLV as a sign of distressed that attracted predatory bugs that ate the caterpillars! This kind of symbiotic relationship between plants and other creatures interests scientists because it shows that plants have developed a sort of language to communicate between them and the animals that help them. Let's hope that nothing that can kill humans ever responds to your lawn's GLVs!