Ethereum supports the transfer and verification of Ether by default. If the target users use Bitcoin more than Ethereum, then interoperability between Bitcoin and Ethereum becomes a problem. To solve this issue, Ethereum has a smart contract that stores and relays Bitcoin transactions so that Ethereum DApps can verify Bitcoin transactions.
In this recipe, you will learn to use BTCRelay, which acts as a bridge between the Bitcoin blockchain and Ethereum smart contracts.
To discover new and popular DApps in the Ethereum network, you can use State of the DApps (https://www.stateofthedapps.com/), which is a DApp registry. You can also submit your own DApp to the registry.