This article is from the Ethernet FAQ, by James Messer James@NetworkUptime.com with numerous contributions by others.
The inteframe gap is the amount of time that is specified between
frames transmitted from a workstation. The designers of the
Ethernet specification arbitrarily chose 96 bit times to occur
between frames from a transmitting station.
This delay is designed to provide the workstations on the Ethernet
network with some 'breathing time' between frames to perform normal
Ethernet housekeeping functions on the network interface card.