Answer:
Colleges offer undergraduate (Associate's and Bachelor's) degrees, as well as sometimes graduate degrees (Master's, PhD, etc.). Many colleges have graduate school sectors within them, whereas a place that is purely a graduate school does not offer Bachelor's degrees at all.
Graduate schools are also specialized and specific. For example, if you attend graduate program to study Bioinformatics, you will only study Bioinformatics. You may also participate in research.
Graduate school comes after undergraduate coursework. You have to have a Bachelors degree to begin a graduate program. Typically, people who are in graduate school are seeking advanced degrees, such as Masters, MBAs, JDs, PhDs, and other specialized degrees.