This is the question that everyone in Industrial/Organizational Psychology hears all the time. Unlike doctor or lawyer or even clinical psychologist, there is not much of a public understanding or branding of what we do. This is partly because the job titles in our field are things like Director of Organizational Development, VP of Human Resources, People Analytics, or just Consultant.
My lab has been working on how each of us can best communicate what we do to different audiences. Most of our parents and friends don't even really know what we do. I like to say that we create customized solutions to complex problems involving people at work. We are experts in measuring people. If you want to come up with a strategic solution to hiring, training, or engaging people at work, you have to measure their skills, attitudes, and personalities. Otherwise you just end up copying Google or another great company. This benchmarking approach can lead to solutions that are wrong for your company.
In an effort to help make I/O Psychology more accessible to more people, I did a podcast on the field and my work in the field. The podcast is called The Psychology of Everything by Dr. Michael McClendon. Check it out, and let me know if you have any more questions about the field!
My I/O Psychology Podcast