-Thread ID values are given as the first column in the output of the
-"notmuch search" command. These are the random-looking strings of 32
-characters.
+A common use of
+.B notmuch show
+is to display a single thread of email messages. For this, use a
+search term of "thread:<thread-id>" as can be seen in the first
+column of output from the
+.B notmuch search
+command.
+
+All messages will be displayed in date order. The output format is
+plain-text, with all text-content MIME parts decoded. Various
+components in the output,
+.RB ( message ", " header ", " body ", " attachment ", and MIME " part ),
+will be delimited by easily-parsed markers. Each marker consists of a
+Control-L character (ASCII decimal 12), the name of the marker, and
+then either an opening or closing brace, ('{' or '}'), to either open
+or close the component.