A single discoverable entity on the iSCSI SAN, such as an initiator or a target, represents an iSCSI node.

Each node has a node name. ESXi uses several methods to identify a node.

IP Address
Each iSCSI node can have an IP address associated with it so that routing and switching equipment on your network can establish the connection between the host and storage. This address is like the IP address that you assign to your computer to get access to your company's network or the Internet.
iSCSI Name
A worldwide unique name for identifying the node. iSCSI uses the iSCSI Qualified Name (IQN) and Extended Unique Identifier (EUI).
By default, ESXi generates unique iSCSI names for your iSCSI initiators, for example, iqn.1998-01.com.vmware:iscsitestox-68158ef2. Usually, you do not have to change the default value, but if you do, make sure that the new iSCSI name you enter is worldwide unique.
iSCSI Alias
A more manageable name for an iSCSI device or port used instead of the iSCSI name. iSCSI aliases are not unique and are intended to be a friendly name to associate with a port.

Each node has one or more ports that connect it to the SAN. iSCSI ports are end-points of an iSCSI session.