Essentially any training program at a community hospital without a lot of academic productivity.
"Low tier" = exclude all NCCN-member/NCI-designated institutions, and all tertiary referral university hospitals
e.g. New York City = MSKCC, Columbia, NYU, Mount Sinai, Cornell, Montefiore are all mid-high tier. Any other program in NYC = "low tier"
Community programs tend to work their fellows harder; more calls, more weekends, busier consults, busier clinics. This is not a negative per se but can be a drain. They also tend to expect less research from applicants and fellows, whether this is a negative or a positive depends on your career goals.