It functions as an accounting information system. It may be developed in-house by the company or organization using it, may be purchased from a third party, or may be a combination of a third-party application software package with local modifications.
Also an accounting software may be on-line based i.e accessed anywhere at anytime with any device which are internet enabled.
Eg; StraightBook, FreshBooks, Xero, QuickBooks Online, Billy, or may be desktop based like QuickBooks, Sage50, Tally etc.