Address
A string of characters identifying where digital assets can be sent, usually derived from a public key.
An address is produced by hashing and encoding a public key: Ethereum takes the last twenty bytes of a Keccak hash, while Bitcoin encodes the hash in base58 or bech32 with a checksum that catches most typing errors. The checksum protects against mistyping but not against sending to a valid address that belongs to someone else, and such a transfer cannot be reversed by anyone. Contract addresses are derived deterministically from the deploying account and its nonce, or from a salt in the case of CREATE2, so an address can be known before the contract exists. Every address's full history is public, which makes addresses pseudonymous rather than anonymous.
In practice
Ethereum addresses use mixed-case checksum encoding, so a wallet can detect a mistyped character before broadcasting a transfer.
The common misunderstanding
An address is not an account at a company and it is not anonymous; it holds nothing by itself, and its entire transaction history is visible to anyone.