OPC UA is the new Unified Architecture for connecting to OPC devices. Probably the best feature of this new standard is that it can be used on any OS, it is not tied to Microsoft like its predecessor is. Many companies make an OPC UA server, and between them grant access to hundreds of driver suites, giving you access to thousands of available devices through Ethernet, serial, and other types of communication. If Ignition doesn't have it already, you can still get your data in.
Connecting to an OPC-UA server is simple (locally or remote), but because of the increased security, you need access to both the OPC server and Ignition to complete the setup. For step-by-step instructions to connect to a Kepware OPC server, see Connecting to Kepware OPC UA. All other OPC UA servers will have extremely similar connection steps.