(As per other sources, the A stands for Accuracy, the C for Completeness)
A transaction is a sequence of »unit of works« whose sum represents an »indivisible logical unit of work«. Transactions are fundamental to (distributed) applications.
Atomicity: all »units of work« or none.
Consistency: a transaction brings the system from one consistent (non contractional) state to another.
Isolation: Effects of »unit of work« are not visible outside the transaction until transaction is completed successfully (see also SQL: Isolation level[isolation level)
Durability: After completion, the transaction will survive system failures.
No track of data history
Note: The ACID properties have no notion of keeping track of data history.
However, such a history is often a requirement for DWHs: What was a customer's amount of open orders on the 7th of May 2014?.
Also, similar requirements for auditing: who deleted/updated which record.