The interviewer wants a brief rundown of not only the jobs
you've had, but also the skills you've gained through these jobs.
Be honest. The level of detail you go into will depend on how
comfortable you feel talking with the interviewer. If you
have many gaps, and filled those gaps with volunteer work,
mention that on your resume. You may head off the question
before it's even asked.
Describe for the interviewer how you chose your objective.
If you've written several resumes with different objectives
on each, be sure you know which one you've sent to this
interviewer.