What is the meaning behind this chant? Who are the eight [types of] individuals that the chant refers to, and what is the meaning of the chant?

Apparently, it is the Wat Phra Ratana Mahathat Monks at evening service before the great bronze Chinnaret Buddha, Phitsanulok Thailand.

Source: Freesound

The translation came from the YouTube comments section but I cannot locate it any longer. Here is the link to a looped version...

Buddhist Chanting


  Of good conduct is the Order of the Disciples of the Blessed One.
  Of upright conduct is the Order of the Disciples of the Blessed One.
  Of wise conduct is the Order of the Disciples of the Blessed One.
  Of proper conduct is the Order of the Disciples of the Blessed One.
  
  This Order of the Disciples of the Blessed One, namely these Four Pairs of persons, the eight [types of] individuals,
  is worthy of gifts,
  worthy of hospitality,
  worthy of offerings,
  worthy of reverential salutation,
  and is an incomparable field of merit for the World.





  Supatipanno Bhagavato sāvakasangho
  Ujupatipanno Bhagavato sāvakasangho
  Ñāyapatipanno Bhagavato sāvakasangho
  Sāmīcipatipanno Bhagavato sāvakasangho
  
  Yadidam cattāri purisa yugāni
  Attha purisa puggalā
  Esa Bhagavato sāvakasangho
  Āhuneyyo
  Pāhuneyyo
  Dakkhineyyo
  Añjalīkaranīyo
  Anuttaram Puññak khettam lokassāti
It's taken from (or quoted in) MN 7 (but it's one of the Pali Formulae -- buddha-vacana.org says, of this one, "45 occurrences", so I suppose this occurs in 45 suttas; also, that it's a component of the Sekha Paṭipadā).

It's one of the Anussati -- specifically Saṅghānussati. Sati is "mindfulness" -- and anu is "after (behind)", "for (towards an aim)", "according to (in conformity with)", also "each/every/one-by-one" -- so, combined, "remember" or "recollect" or "call to mind".

AN 3.70 says (of all the Anussati) that, "as they recollect ... their mind becomes clear, joy arises, and mental corruptions are given up".

Commentary says that this is referring to the "ariya sangha" (the noble sangha), i.e. all enlightened ones. The "8 [types of] individuals" refer to the "four stages of enlightenment" (sotāpanna etc.) or as it says "the four pairs of persons" -- both ordained and/or lay.