19. Crypto wallets have a public and a private key to identify them. When you want to transfer crypto to another wallet (yours or someone else's), which of the keys of the destination wallet do you need?
From Quiz Introduction to Cryptocurrency
Answer:
Public
Pretty self explanatory, the public key, or address of the wallet, is visible to everyone, while the private is only viewable to the wallet's owner. The public key is what you need to know when transferring crypto to any wallet. For that matter, consider it as a bank account number: you need to enter the key to the wallet you wish to transfer to. Together with the private key, they serve as a means to validate the transactions in the crypto world.
The public key also consists of a hash code, and it's generated automatically when the wallet is created. You have to be extremely careful when entering the address, because one single typo can send your funds to an unknown wallet, and it's pretty much impossible to trace them and get them back. Many of the apps offer an option to copy the address, or to retrieve it through a QR code, to minimize the risk of errors when transferring.
The private key, on the other hand, is vital to the wallet's owner. It consists of a set of random words (12 to 24 on some wallets) that must be entered in the same order to grant full access to that wallet in any device. Needless to say, private keys are the main objective of hackers, since they can gain control of any wallet (and thus, any crypto contained within) by knowing their private keys.
When using a hot wallet, the risk of theft of the private keys is increased, due to the wallet being constantly online. Having a wallet within a web-based exchange makes them even more vulnerable, as an attack on the whole site can target numerous wallets at once. Most web exchanges issue an explicit disclaimer about their responsibility for the safety of the funds of every user.