Context is an object that contains the information for the sending and receiving service, or execution unit, to correlate one signal with another.
For example, if service A calls service B, then a span from service A whose ID is in context will be used as the parent span for the next span created in service B. The trace ID that is in context will be used for the next span created in service B as well, which means that the span is part of the same trace as the span from service A.