What actually is an OPC UA client

generalStandard 2017 UA Server Profile, Node Management Server Facet, Client Redundancy Facet, Redundancy Visible Server Facet, Query, Reverse Connect Facet, Request State Change Server Facet, Global Certificate Management Server Facet, User Role Base Server Facet, User Role Management Server FacetData accessDataAccess Server Facet, Complex Type 2017 Server Facet, Durable Subscription Server FacetEventsStandard Event Subscription Server Facet, Address Space Notifier Server Facet, Auditing Server FacetMethodsMethod Server Facet, State Machine Server Facet, File Access Server FacetAlarms & ConditionsA&C Base Condition Server Facet, A&C Address Space Instance Server Facet, A&C Enable Server Facet, A&C Alarm Server Facet, A&C Acknowledgeable Alarm Server Facet, A&C Exclusive Alarming Server Facet, A&C Non-Exclusive Alarming Server Facet, A&C Previous Instances Server Facet, A&C Dialog Server Facet, A&C AlarmMetrics Server Facet, A&C Refresh2 Server FacetHistorical AccessHistorical Raw Data Server Facet, Historical Aggregate Server Facet, Historical Data AtTime Server Facet, Historical Access Modified Data Server Facet, Historical Annotation Server Facet, Historical Data Insert Server Facet, Historical Data Update Server Facet, Historical Data Replace Server Facet, Historical Data Delete Server Facet, Historical Access Structured Data Server Facet, Base Historical Event Server Facet, Historical Event Update Server Facet, Historical Event Replace Server Facet, Historical Event Insert Server Facet, Historical Event Delete Server Facet