SAN stands for Storage Area Network and is defined as the network that moves data from hosts to storage (arrays, tape devices, etc.). This is typically a dedicated network (always dedicated in a Fibre Channel SAN, as a best practice in an iSCSI or hybrid SAN). A storage array is one of the storage devices to which a SAN connects hosts, and is usually considered a component of the SAN.
I hope this helps,
If you understand LANs, then the best way to understand SANs is to compare the two.
LAN- NICs, Ethernet Cables, Switches, Ethernet Cables, and finally NIC's at the other end.
SAN- HBA, Fibre Cables, Fibre Switches, Fibre Cables, and finally disks on the other end which actually hold the data.
These disks are packaged together by vendors, and put in large boxes, and called storage arrays.