extend glossary

Signed-off-by: Florian Lehner <[email protected]>

Author: florianl

specification/glossary.md

@@ -68,7 +68,7 @@ The maintainer of an OpenTelemetry SDK Plugin, written against OpenTelemetry SDK
 ### Signals
 
 OpenTelemetry is structured around signals, or categories of telemetry.
-Metrics, logs, traces, and baggage are examples of signals.
+Metrics, logs, traces, profiles, and baggage are examples of signals.
 Each signal represents a coherent, stand-alone set of functionality.
 Each signal follows a separate lifecycle, defining its current stability level.
 
@@ -228,3 +228,18 @@ library into OpenTelemetry using the [Log API](./logs/api.md). The
 terms "log bridge" and "log appender" are used interchangeably, reflecting that
 these components bridge data into OpenTelemetry, but are often called appenders
 in the logging domain.
+
+## Profiles
+
+Profiles describes the OpenTelemetry signal.
+
+### Profile
+
+In the context of the profiles signal, profile holds one or more stacktraces of
+a OpenTelemetry instrumentation scope.
+
+
+### Profiling
+
+Profiling describes the process of collecting data that will be reported with
+the profiles signal.