What is ACID property of transactions in Relational Database?

In Relational Data Bases ACID stands for
Atomicity
Consistency
Isolation
Durability

Atomicity
means the transaction in RDBMS should be atomic, it should not be further split in smaller units to handle. Modification on the data in the database either fail or succeed. If one part of the transaction fails, the entire transaction to be fail. A software crash entails an implicit rollback.

Consistency
Only valid data (valid according to integrity constraints) may be commited in RDBMS. If, for some reason, a transaction is executed that violates the database’s consistency rules, the entire transaction will be rolled back and the database will be restore to a state consistent with those rules.

Isolation
One transaction does not interfere with another. All the transactions in RDBMS should execute in their own transaction space.

Durability
A commited transaction will not be lost. It should be permanent in database.

Note : Oracle uses the redo log and undo to make ACID possible.