Tags are the placeholders for information in SCADA servers; they're similar to OPC items, except that they can be used for both internal (results of SCADA script computations, for example) and external (information from PLCs or OPC servers).
The term "Tag" is used in SCADA and simply means "variable" in computer language. SCADA stands for supervisory control and data acquisition in industry.
I/O tags (external), virtual tags (internal), and runtime (memory) tags are the three types of tags used in SCADA.
A tag is a name you give to a device/address. PLC's Depending on the manufacturer of the device/PLC, it is also known as "variable" or "symbol."
Without using logic, a produced tag provides its data to one or more consumed tags (consumers). Tag "consumed" A tag that receives data from a previously generated tag. The data type of the consuming tag must match the data type of the created tag (including any array dimensions).