Observerships: Refers to shadowing-only rotations, no direct patient-care.  These programs are open to both medical students and graduates (IMGs) and can take place in a variety of settings: hospitals, clinics, ambulatory care, urgent care, etc.

Externships: These programs are only open to graduates and involve more hands-on patient interaction.  While these programs are not eligible for medical school credit, since they are only open to IMGs, they often follow a similar educational curriculum to clerkship rotations.