locking differential and differential lock are not the same

Only few vehicles in the US are offered stock with front and rear differential locks: Dodge Powerwagon, Hummer H2 + H3, Jeep Wrangler Rubicon, Mercedes G500.

On some models a rear differential lock is optional: Porsche Cayenne, VW Touareg, some Mitsubishi, some Toyota.
Other terms used for differential locks are: locker, diff locks, diff lockers, differential lockers

Unfortunately, limited slip differentials (LS), available as options for many 4x4 in the US are offered by sales people as "locking differentials". A confusing term because nothing on these differentials is LOCKING. They are by far inferior to a differential that is truly (manually or automatically) lockable.
If you have to decide whether to get a "locking differential" aka limited slip (LS), if available as an option on your new truck, I would recommend getting it, because it is still better than not having anything at all.

To repeat: "locking differentials" are limited slip differentials that are not to be confused with differential lock!

Differential lock = differential locker = diff lock = diff locker = locker

It seems to me, that manufacturers and dealers prefer to use the term "locking differential" over the correct term "limited slip differential" because it sounds more like the real thing - even though it is not. Is this already consumer fraud?

Now here is a twist to the locking differential story: When Chevy advertises its trucks with an optional rear locking differential - it indeed is a differential that locks up (automatically). In the 80's it was sold as a Gov-Lok for a while named Command-Traxx and is available in some Chevy trucks as G80 option. It is not manually activated as in Dodge, Jeep and Mercedes - it locks up automatically. It is a hybrid of a clutch type limited slip unit combined with a flyweight governor that is able to lock up 100%.

In addition to factory installed diff locks, there are several aftermarket options to add a differential lock to front and rear axles. ARB Air Locker, Detroit Locker, Eaton Locker are probably the best known. Recently we saw some newcomers like the OX Locker which seems like a copy of a long know German Schwarz locker to me.