Blockchains work by their own rules and in isolation from the outside world. The Cosmos network aims to enable blockchains to interact with each other, making transactions between blockchains. Cosmos runs the coordination and verification center called the Cosmos Hub for the whole system to work in harmony. Tendermint transactions occurring in the Cosmos network are verified with the Proof of Stake (PoS) algorithm.
You can also store your ATOM balance in portable and secure hardware wallets that are not constantly connected to the internet. In order to send ATOM from hardware wallets, you need to connect the device to your computer and perform transactions through the wallet application.
All you need to know about Cosmos (ATOM)