It is a board of engineers (which will become your peers) to ask about specific categories of skills. You don't need to know everything but it helps to be well rounded.

I received an email to attend a hiring event here in Florida where multiple managers, recruiters and positions would be available. I arrived early and dressed in business attire. There were over 200+ potential employees with notebooks prepared for an "elevator speech". I located the position I wanted and spoke with a panel of managers in private. The Interview began with personality-based questions attempting to break the ice and build some familiarity with each other. I brought several resumes copies and individually handed it to each supervisor. We went over my skills & experience and dove into more technical based questions from there. I highly encourage you be prepared and familiar with your resume. I did not know the answer to all the technical questions they asked and wrote the question down with the name of the person that asked it. I later in the week was able to get a hold of each one and gave them their response as well as an update on my latest achievement that highly encouraged their decision in sending me an offer.