what is the 'private key'?
The private key is a code enabling you to access coins or tokens on the Blockchain. The Private Key is like a certificate of ownership. Accordingly it should not be exposed to anyone else. every transaction performed on the Blockchain is signed with the private key. Of course the signature is not exposing the exact number as this would result in security threat of wallets but both, the public key and public address derive from it. Even though the public key and address are both originating and calculated through the private key. Mathematical functions make it impossible to identify the private key from its public key or public address.
how to safely store your 'private key'?
The most secure method is to directly right it down on apiece of paper then storing it in a treasury at home or even in a safe deposit box on your local bank. Make sure that you do not keep your private key on any electronically devices connected to the internet. As well storage on a secondary computer with no internet connection is not a safe method for long-term retention.A Computers’ risk to crack down rises immensely the older they get.
Even though you probably wanna have the highest possible security standard you have to choose a middle way fitting your personal needs. Many people want to regularly access their wallets, making transactions. Physically stored private keys reduce accessibility and might therefor not be the best solution for everyone. It is obvious that the purchase of physical hardware wallets is going to be the safest way. In this case the physical device itself represents your private key and can be accessed but also restored at any time.