What is the difference between CV and Resume?

Resume is shorter.

Resume provides a summary of your education, previous employment, skills, and accomplishments.

CV includes all the above in more details plus publications, presentations, detailed teaching experience, etc.

A resume tends to be a one page summary of what your background is with respect to the position you are applying for. informally needs to be a very dumbed-down version of what you have done so it can be understood by a general audience specially the early-stage selection committees(read departments staff, random volunteers, HR personnel). In a resume, a person might focus on marketing his accomplishments in a context of the positions this person is submitting the resume to.

CV or curriculum vitae can go any number of pages and can include all aspects of you. I have heard people having 150 pages of CV and using them for applying to positions like a program manager at NIH with 40 pages for their publications alone. A CV is in a way an absolute document and you don't edit it based on the position you submit your CV to. It is generally all there is to it.