We are all industrial engineers but this is honestly a pretty difficult question to answer without sounding vague or just rattling off examples. Say you are at a job interview (not industrial engineering related) and the interviewer asks what industrial engineering is. What is the best response to this question?
I’ve always said something along the lines of “improve processes and make things more efficient”. Then you can go into specific examples (determining the route of mail truck driver to use minimal gas, etc.). Usually, that’s enough for them to get the gist, and then they can ask more questions if they need to.
I would say something similar to what Jessica mentioned. I usually also add that Industrial Engineers work in a variety of fields and are not restricted to process/efficiency improvements in traditional manufacturing fields, as some might think (For example, healthcare, business strategy etc.).