What is the Mindstorms NXT Education kit?
There is an educational version. It is set number 9797.
The NXT 2.0 set is set 8547.
Both come with:

1 - NXT brick
3 - Motors
1 - Ultrasonic range sensor
2 - Touch sensors
1 - 20 cm cable
4 - 35 cm cable
2 - 50 cm cable

The NXT 2.0 has some things the education set does not:

1 - color sensor
1 - Test Mat
Software (The education software is sold separately! from the educational set)

The education set has some things the NXT2.0 set does not:

1 - Light sensor
1 - Sound Sensor
1 - Rechargeable battery module
1 - AC adapter for rechargeable battery module
3 - Converter cables suitable for use with original Mindstorms accessories or 9V Technic motors and light bricks
2 - 9V Technic light bricks
1 - Durable storage system

The two sets also come with different assortments of pieces, with the educational one contained fewer total pieces, with more that would integrate with original Mindstorms or Technic kits.
The education kit is designed to used in conjunction with an existing parts collection,
or with an Educational resource kit, basically bulk parts. Two such kits exist. Both come in a storage system much like the educational kit.
Set 9648 contains an assortment of traditional Technic style parts with a slight emphasis on the studless beams, but still containing many studded components.
Set 9695 is newer and has more parts, with a strong emphasis on studless design. Relatively few parts have studs.