From The Free On-line Dictionary of Computing (19 January 2023):
Internet Access Provider
IAP
provider
<networking, company> (IAP) A company or other origanisation
which provides access to the Internet to businesses and/or
consumers. An IAP purchases an Internet link from another
company that has a direct link to the Internet and resells
portions of that bandwidth to the general public.
For example, an IAP may purchase a T1 link (1.544Mb/s) and
resell that bandwidth in chunks consisting of ISDN (64Kb/s,
128Kb/s) and analog modems (14.4Kb/s, 28.8Kb/s). The IAP's
customer base is likely to include both businesses and
individuals. Individual customers usually connect to the IAP
via a modem and telephone line to a (preferably local) point
of presence.
An IAP may also be an Internet Service Provider.
(1996-06-25)