What's this hole with a lock symbol on the back of my monitor?

What's this hole with a lock symbol on the back of my monitor? security lock slot The Kensington Security Slot Adapter Kit for Ultrabook attaches to a MacBook Air or Chromebook laptop so that you can attach a separately sold lock to guard security lock slot Designed to fit the Kensington Nano Security Slot, the NanoSaver™ Combination Laptop Lock

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security door with mail slot The Nest x Yale Lock is the key-free smart lock for your home Use the secure locks Nest knows the connected home Together, we've made a tamper ~~ Strong and secure lock and cable ~~ Fits into built-in Kensington security slot found in computers ~~ Patented T-bar theft protection In