What is a the difference between a "Job Fair" and a "Career Fair"?
They can be the same thing depending on who's running them. In general, here is a definition that you can use:
A Career Fair generally is an event where companies will participate to attract candidates to pursue a career in their field or organization - they usually will accept your resume for future consideration. It is an opportunity for people and organizations to get to know each other. Educational organizations may also be in attendance to discuss educational upgrading or specific training programs.
A Job Fair generally is an event where companies will participate to collect the resumes of qualified candidates to staff specific current vacancies in their organization.