Only a handful of vehicles made in certain years, from a few manufacturers use a CK wired socket. Sometimes different car and truck manufacturers will change the type of wiring configuration they'll use to power certain turn signal and brake light bulbs. Normally you would have Positive and Negative terminals on either side of the bulb, but the "CK" type wiring is different.
A CK/SRCK is like the traditional sockets you see in most Japanese, and American vehicles except it's wired like this:
These 2 types of wiring configurations can be found on 3157 or 7443 types of bulbs. The position of the contacts in the socket is the only difference. The bulbs and the sockets look identical - the only way to know the different is to test with a multimeter!
If you install a non-compatible bulb there's a possibility it will blow the protection circuit fuse and you will have to replace the fuse and install the correct bulb. Sometimes if you use the wrong bulb it will simply not work correctly, without blowing a fuse - that depends on the vehicle.
Here is a list of possibly confirmed vehicles that use CK style sockets: