CrossSearch uses the Ulrichsweb's classifications of journals. Scholarly describes the primary audience for the publication. Peer-reviewed "refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board."
Most peer-reviewed/refereed publications are also Academic/Scholarly serials, but it is possible for a publication to have one designation but not the other.
For a fun way to find out more about this, watch the Library's iResearch video Scholarly versus non-scholarly resources, and check out the eSearch to Research online tutorial for new students. There are modules covering four different disciplines (Arts, Education and Social Work, Law, and School of Business). The information in each is very similar but the examples are discipline-specific. Choose the most appropriate discipline for you.