Atomicity, Consistency, Isolation, Durability - properties that guarantee database transactions are processed reliably. Like having strict rules that ensure bank transfers either complete fully or not at all.
When you transfer money between accounts, ACID properties ensure the money is either transferred completely or the transaction fails entirely.
ACID is a database transaction guarantee (a property of a database engine), not a standalone cloud service. Many managed relational databases across AWS, Azure, GCP, and OCI support ACID transactions (especially for single-database transactions) depending on the specific engine and configuration.