What is a Kensington Lock?

Which lock do you use? I've always thought the kensington locks on laptop were

Kensington Lock slot; Power Supply – 19V via DC jack; Dimensions – 117 x 112 x mm; Weight

kensington security slot™ This easy-to-use cable lock works on any Lenovo equipment with a security slot, protecting your device To check if the Lock is compatible with your system,

kensington nano security slot™ Designed to fit the Kensington Nano Security Slot, the NanoSaver™ Combination Laptop Lock