If you want to use transactions with MySQL, you will have to use InnoDB engine, because the default engine on MySQL 5.1 (MyISAM) does not support transactions. Otherwise, if you use MySQL 5.5 you do not have to worry about it, because default engine is InnoDB.
A transaction is a set of SQL instructions which are run as a unit and can be cancelled if it is required.There are confirm and cancel operations
Transactional systems are characterized by their features:
Atomicity: Transaction’s instructions form a logic unit.
Coherence: Database must coherent before and after transaction. Can’t affect negatively.
Isolation: Transactions are not affected among them
Durability: If the transaction was executed succesfully, changes will be stored permanently.
To start a transaction you can use BEGIN or START TRANSACTION
To create a savepoint use SAVEPOINT savepointname
And for rollback use whether ROLLBACK (to return to the BEGIN point) or ROLLBACK TO savepointname (to return another specific point)
Example of use: