The biggest danger in bitcoin security is the individual user perhaps losing the private key or having the private key stolen. Without the private key, the user will never see her bitcoins again.
Hot Wallet
Hot wallets are wallets that run on internet-connected devices like computers, phones, or tablets. This can create vulnerability because these wallets generate the private keys to your coins on these internet-connected devices.
Cold Wallet
These wallets store a user’s address and private key on something that is not connected to the internet and typically come with software that works in parallel so that the user can view their portfolio without putting their private key at risk.
Physical Coins
The coin you purchase will have a tamper-proof sticker covering a predetermined amount of Bitcoin. In order to purchase the physical coin, you may need to pay a slight premium over the value of the Bitcoin that you’re buying, owing to the cost of the manufacture and shipment of the coin itself.