doc/exceptions: clarify ambiguous terminology

The terms 'inspection' and 'detection' were being used to signify
different engine actions in this document, while throughout the
documentation and code they're many times interchangeable.

Replace 'inspection' with 'parsing' or even 'decoding and parsing' as
more appropriate.

Add a small glossary to clarify what we mean with those terms.

doc/userguide/configuration/exception-policies.rst

@@ -111,13 +111,13 @@ documentation).
 The possible values for the exception policies, and the resulting behaviors,
 are:
 
-- ``drop-flow``: disable inspection for the whole flow (packets, payload,
+- ``drop-flow``: disable decoding and parsing for the whole flow (packets, payload,
   application layer protocol), drop the packet and all future packets in the
   flow.
 - ``drop-packet``: drop the packet.
 - ``reject``: same as ``drop-flow``, but reject the current packet as well (see
   ``reject`` action in Rule's :ref:`actions`).
-- ``bypass``: bypass the flow. No further inspection is done. :ref:`Bypass
+- ``bypass``: bypass the flow. No further decoding or parsing is done. :ref:`Bypass
   <bypass>` may be offloaded.
 - ``pass-flow``: disable payload and packet detection; stream reassembly,
   app-layer parsing and logging still happen.
@@ -144,8 +144,8 @@ midstream pick-ups enabled or not and the various exception policy values:
      - Midstream pick-up sessions ENABLED (stream.midstream=true)
      - Midstream pick-up sessions DISABLED (stream.midstream=false)
    * - Ignore
-     - Session tracked and parsed, inspect and log app-layer traffic, do detection.
+     - Session and app-layer traffic tracked and parsed, log app-layer traffic, do detection.
-     - Session not tracked. No app-layer inspection or logging. No detection. No stream reassembly.
+     - Session not tracked. No app-layer parsing or logging. No detection. No stream reassembly.
    * - Drop-flow
      - Not valid.*
      - Not valid.*
@@ -156,14 +156,14 @@ midstream pick-ups enabled or not and the various exception policy values:
      - Not valid.*
      - Session not tracked, flow REJECTED.
    * - Pass-flow
-     - Track session, inspect and log app-layer traffic, no detection.
+     - Session and app-layer traffic tracked and parsed, log app-layer traffic, no detection.
-     - Session not tracked. No app-layer inspection or logging. No detection. No stream reassembly.
+     - Session not tracked. No app-layer parsing or logging. No detection. No stream reassembly.
    * - Pass-packet
      - Not valid.*
      - Not valid.*
    * - Bypass
      - Not valid.*
-     - Session not tracked. No app-layer inspection or logging. No detection. No stream reassembly.
+     - Session not tracked. No app-layer parsing or logging. No detection. No stream reassembly.
    * - Auto
      - Midstream policy applied: "ignore". Same behavior.
      - Midstream policy applied: "ignore". Same behavior.
@@ -182,11 +182,11 @@ whole flow.
      - Midstream pick-up sessions ENABLED (stream.midstream=true)
      - Midstream pick-up sessions DISABLED (stream.midstream=false)
    * - Ignore
-     - Session tracked and parsed, inspect and log app-layer traffic, do detection.
+     - Session and app-layer traffic tracked and parsed, log app-layer traffic, do detection.
-     - Session not tracked. No app-layer inspection or logging. No detection. No stream reassembly.
+     - Session not tracked. No app-layer parsing or logging. No detection. No stream reassembly.
    * - Drop-flow
      - Not valid.*
-     - Session not tracked. No app-layer inspection or logging. No detection. No stream reassembly.
+     - Session not tracked. No app-layer parsing or logging. No detection. No stream reassembly.
        Flow DROPPED.
    * - Drop-packet
      - Not valid.*
@@ -195,14 +195,14 @@ whole flow.
      - Not valid.*
      - Session not tracked, flow DROPPED and REJECTED.
    * - Pass-flow
-     - Track session, inspect and log app-layer traffic, no detection.
+     - Track session, parse and log app-layer traffic, no detection.
-     - Session not tracked. No app-layer inspection or logging. No detection. No stream reassembly.
+     - Session not tracked. No app-layer parsing or logging. No detection. No stream reassembly.
    * - Pass-packet
      - Not valid.*
      - Not valid.*
    * - Bypass
      - Not valid.*
-     - Session not tracked. No app-layer inspection or logging. No detection. No stream reassembly.
+     - Session not tracked. No app-layer parsing or logging. No detection. No stream reassembly.
        Packets ALLOWED.
    * - Auto
      - Midstream policy applied: "ignore". Same behavior.
@@ -325,6 +325,15 @@ The available command-line options are:
 - ``simulate-alert-queue-realloc-failure``: prevent the engine from dynamically
   growing the temporary alert queue, during alerts processing.
 
+Glossary
+========
+
+- **decoding**: traffic parsing on the packet level;
+- **[app-layer] parsing**: traffic is parsed on the application layer level for
+  events, anomalies and logging;
+- **detection**: evaluate traffic against loaded rules to generate alerts and/ or
+  block or allow traffic.
+
 Common abbreviations
 --------------------