In the world of business, cold storage (otherwise known as a cold wallet) is a digital wallet not connected to any internet network. While this does limit the availability one has to access the contents of said wallet, it also limits vulnerabilities to cyber attacks and data breaches an internet connection would inherently have.
Cold storage is particularly useful for cryptocurrency traders and investors, as they can protect their investment.
In a broader definition, cold storage can be a data archive which is defined by not being immediately accessible, and is predominately used for inactive data, or backups.
In an even broader definition, cold storage is a refrigerator.