1. according to presence:
    • in-person
    • distance
  2. according to formality:
    • formal
    • non-formal
    • informal
  3. according to the number of participants:
    • group
    • individual
  4. according to the payment:
    • with a fee
    • free
  5. according to age:
    • adult
    • children/youngsters
  6. according to the characteristics of the groups:
    • homogenous
    • heterogenous
  7. and so on