The 'Explain your PhD' question is probably more about are you good at communicating difficult issues at an appropriate level or not rather than anything else. The right approach is mainly to be obviously enthusiastic and quickly work out what common ground you have with your audience in order to relate it to what they already know.
This. It's an important exercise to explain your work without using jargon to folks outside your field. Clearly your work is interesting if you spend your time doing it. Knowing how to relate this interest and enthusiasm to others is a really good skill to have regardless of whether you're industry bound or not.
Probably means different things to different people but, in my case, it means supervising someone and being responsible for appraisals and work direction. Hope that helps!