There are three Linux drivers for Intel network cards. I spent all day tracking down the differences.

This release includes three Linux* Base Drivers for Intel(R) Gigabit Network Connections.

* igb driver supports all 82575 and 82576-based gigabit network connections.
* e1000 driver supports PCI and PCI-X gigabit network connections.
* e1000e driver supports all PCI Express gigabit network connections, except those that are 82575 and 82576-based.

Borrowed from intel.com, driver downloads.