What is the Kensington lock used for? How is it used?

What's this hole with a lock symbol on the back of my monitor? security lock slot Keep your devices secure with the Lock Slot Adapter Designed for use with devices and monitors without a security lock slot security lock slot We offer a selection of accessories to cater to your device and hardware security needs, including key operated and combination slot locks

security cable slot Rocbolt® Security Slot Adapter Kit – Security Anchor Point – Nylon + 30% Fiberglass – Kit Includes Anchor Point, Glue & Alcohol Pad – 3M™ Dual Tape Adhesive