Nodes in OPC Classic are identified either by Item IDs, or using browse paths.

Item Ids (or Node Id) are the primary way.

An alternative way (to using a node ID) of specifying a node in OPC address space is using a browse path. The browse path is a sequence of node names, starting from a known location (e.g. the root of the OPC address space). The browse path can also be expressed as a string, where the individual node names are separated by delimiters (e.g. “/”, a slash).

Browse paths can be absolute (starting from a specified node), or relative.

The advantage of the browse paths is that you can construct them yourself, with just knowledge of the node names, without knowing the full node IDs. In the end, each item must be addressed by its node ID, and OPC Data Client will resolve the browse path to a node ID as necessary.