In the Bitcoin blockchain, transactions are not so simple, transactions are actually completed through scripts to carry more functions, which is why Bitcoin is called a "programmable currency".
A Bitcoin transaction is a script that first unlocks the UTXO through the private key (often called an unlock script: Signature script), which is also called transaction input.
The output of the transaction points to a script through the public key, which expresses: whose signature (signature is a common form, not necessarily a signature) can match the output address, the money will be paid to whom.
Each Bitcoin node will verify a transaction by executing the unlocking and locking scripts at the same time. If the result of the script combination is true, it is a valid transaction.
Common types of Bitcoin transaction scripts (Pay-to-Public-Key-Hash) combinations.
Since transactions are implemented through scripts, the scripting language can express countless variants of conditions.
However, since Bitcoin's scripting language is not Turing-complete, and the transaction mode is still limited, Ethereum was created to solve this problem.