Distributed trace
A distributed trace is a set of events, triggered as a result of a single logical operation, consolidated across various components of an application. A distributed trace contains events that cross process, network and security boundaries. A distributed trace may be initiated when someone presses a button to start an action on a website - in this example, the trace will represent calls made between the downstream services that handled the chain of requests initiated by this button being pressed.
Opaque value
An opaque value refers to a value that can only be understood or processed in any way by the distributed trace participant that generated this value. Any other participant must treat it as a blob of bytes.