Chicago’s core is actually something of a hybrid. There are 8 areas addressed by Chicago’s General Education requirements, and they really span a spectrum from very core-like to pure distribution requirement. However, the core-like elements are very strong, and pretty much represent what people are taking about when they refer to Chicago’s Core Currlculum.
The General Education requirements address the following:
Humanities. There is a very limited set of courses that satisfy this requirement, and they have a lot of overlap in what their syllabi. So students can choose from a list of options, but there is a set of specific texts that everyone will be studying, albeit in different order and with somewhat different focus. And there is another set of texts that 80% of everyone will have studied. 100% of students take 2-3 quarters of this in their first year at Chicago.
Social Sciences. Similar to Humanities, a limited set of courses with enormous overlap. Everyone has to take three quarters, no exceptions. Sosc and Hum are really the core of the Core.
Arts. Students are required to take 1-2 quarters of arts-related courses. Not every arts-related course offered by the university qualifies, but unlike Hum and Sosc there is no real overlap. Things that count tend to be entry-level performance/production classes, and "history of . . . " or “theory of . . .” surveys. No placing out.
Civilization. Students take 2-3 quarters of Civ, usually a single course. For lots of students, this is integrated with study abroad. A very wide range of Civ classes is offered, and there is no real common content, but there is a common interdisciplinary approach, in which the courses tend to cross departmental lines. I think some Civ courses can be taken for credit in a specific major (although you can’t double up on major credit and Core credit with the same course), but many cannot and remain outside the normal structure of academic departments. No placing out.
Math. Students are required to take 2 quarters of math at roughly the level of calculus. The requirement can be met with AP credit or a placement test. This is effectively a distributional requirement.
Physical science. Students are required to take 2 quarters of physical science. The standard introductory courses in Chemistry and Physics qualify, but the college also offers special interdisciplinary courses that satisfy this requirement for non-STEM types who do not want to take one of the pre-med courses. I think you can also place out of this with AP or placement test credit. So, effectively a distributional requirement. Note, however, that the number of courses offered that people take to satisfy this requirement is not much larger than the number of options for meeting the Hum or Sosc requirement.
Biological science. Same as physical science, except I think you can only place out of 1 quarter. (I am not sure about that.)
Foreign Language. Everyone is required to take three quarters of a foreign language or to demonstrate equivalent competence through standardized tests (AP or SAT II) or special qualification tests. A distributional requirement.
If you don’t place out of anything, the General Education requirements would require about 19 courses (out of 42 required to graduate), or about 40% of your college coursework. Slightly more than half of that is either very core-like or significantly core-like, and the remaining half is basically distribution requirements.