There are two main families.

Enhancement - where the mosfet has to be forward biased like a transistor.

Depletion - where the mosfet is reverse biased like a thermionic valve (tube in the USA).

Some mosfets have two gates (dual gate mosfets) and are commonly used as r.f. mixers.

The insulating layer is extremely thin and can be easily damaged by static.
Antistatic precautions must be taken when handling them.
Soldering iron tips must be earthed.
The operator must be grounded via a high value resistor, with wriststraps etc.
The workplace must be grounded safely.
Components must be handled with care.
I usually touch some earthed point just before handling static sensitive devices.

Some devices have Zener diodes built in, between gate and source, for protection.