There is a huge difference between vertical and horizontal reservations which is listed below:
~Vertical reservation:
Vertical Reservation is a reservation for people from lower socioeconomic classes like SC/ST/OBCs.
~Horizontal reservation:
It is a reservation for children of veterans who are serving in the armed forces, have retired, or have been killed in action, as well as disabled people, widows and unmarried women, and people from rural areas.