One example of this is a type of wasp which kills the larvae of many other insects. Most however, cannot sting people, what looks like a stinger is actually a long tube through which they lay their eggs. They use it to put the eggs either on or in insect larvae. When the eggs hatch, the wasp larvae eat the inside of their host, killing it. This controlls the population of many damaging insect and hence, what may not be a very nice looking insect, is really very very helpful.
Some insects make materials which people like to use.
In many parts of the world people eat insects, but this is relatively uncommon in North America. Some of the insects people around the world eat include beetles, moths, and many types of insect larvae. Even though North Americans do not often eat insects, many of the animals they do eat feed partially or wholly on insects. Either way, insects play a major role in the food sources people use.