Quote from Erudite on ,

OND stands for - Ordinary National Diploma
OND or ND is a polytechnic award for a two-year course with which the holder can be employed or be offered admission into Higher National Diploma (HND) and where through Direct entry admission, be admitted to 200 level course in a university.

HND stands for - Higher National Diploma
HND is the award given to a polytechnic graduate after completing a 2-year National Diploma, 1 or 2 years Industrial Training (IT) and 2-year Higher National Diploma course.

Note that the HND course doesn’t require writing UTME again or obtaining the JAMB direct entry form. Applicants are only to take part in the school’s organized entrance test and interview or screening.