What is a public key in Bitcoin?

In the context of Bitcoin, a public key serves as an address for receiving Bitcoin. When a user wants to receive funds, they provide their public key, which is derived from their private key. This public key is mathematically linked to the private key but does not reveal it, ensuring the security of the wallet. The public key can be hashed to create a Bitcoin address, which is the actual string of letters and numbers shared with others to receive payments.

While the other choices present useful concepts in the Bitcoin ecosystem, they pertain to different functionalities. A secret number for wallet access refers to the private key, which is essential for signing transactions and accessing funds. A verification code for transactions can be associated with the signature created using the private key, but it is not specifically termed as a public key. The unique identifier for miners does not relate to the public key; miners are primarily identified by their mining addresses or the hashes of the blocks they produce.

Thus, recognizing the public key as an address for receiving Bitcoin is fundamental to understanding how Bitcoin transactions work and how users interact with the Bitcoin network securely.