Hi...
One of the major differences while comparing MBA and PGDM is that MBA or Master of Business Administration is a degree course that can only be offered by the colleges affiliated to universities, whereas PGDM or Post Graduate Diploma in Management is a diploma course offered by autonomous institutes.

The Faculty of Management Studies (FMS), Delhi, is affiliated to Delhi University and hence offers an MBA degree. While MBA colleges likeSP Jain Institute of Management Studies and Research (SPJIMR) or Management Development Institute, Gurgaon are autonomous in nature and hence offer PGDM courses.

MBA vs. PGDM Differences
MBA and  PGDM Eligibility

The full-time graduate degree of minimum three years duration.

Different colleges set different cut-offs for percentage secured in graduation. However, on a broad basis, 50% is the accepted percentage level.

Candidate appearing in the final year of bachelors degree/equivalent qualification is eligible for the admission, provided he/she can produce a letter from their colleges head confirming about their present status as claimed.

Entrance Exams CAT, MAT, GMAT, IIFT, SNAP, IRMASAT, XAT, CMAT, NMAT, etc.

Qualification  MBA Degree course
PGDM Diploma course

Course Structure and Approach
MBA
University approved curriculum, hence, mostly theoretical based and uniform across institutes affiliated to a university.
Mostly semester-based system.
PGDM
Industry oriented program focused more on building soft skills.
Mostly trimester-based system.

Accreditation
MBA
Accredited by University Grants Commission (UGC)
PGDM
Accredited by All India Council for Technical Education (AICTE)
Perception
Both MBA and PGDM are viewed as equivalent during recruitment. The influencing factor is mostly the institute offering it. Also, while PGDM courses might be industry-oriented and preferred by the corporates, they might have to face roadblocks while applying to pursue higher education or jobs overseas