It is another component of Oracle Grid infrastructure and is installed at the same time into the same oracle home directory as oracle clusterware software.
Oracle ASM provides the cluster-aware shared storage and volume manager for RAC database files. It also provides shared storage for Oracle Clusterware Registry (OCR) and voting disks.
Oracle ASM is an oracle’s recommended storage management solution and is an alternate to conventional volume managers, raw devices and file systems. And supports both single instance oracle database and real application clusters (RAC) configurations.