Hi, I hope this works (and is correct), it's the first time I dare ...
diff --git a/doc/org.texi b/doc/org.texi
index d508c06..c229187 100644
--- a/doc/org.texi
+++ b/doc/org.texi
@@ -15563,13 +15563,18 @@ execution.
@cindex @code{:session}, src header argument
The @code{:session} header argument starts a session for an interpreted
-language where state is preserved.
+language where state is preserved. By default, a session is not started.
-By default, a session is not started.
-
-A string passed to the @code{:session} header argument will give the session
-a name. This makes it possible to run concurrent sessions for each
-interpreted language.
+@itemize @bullet
+@item @code{none}
+The default. Each block is evaluated in its own session. The session is
+not preserved after the evaluation.
+@item @code{other}
+Any other string passed to the @code{:session} header argument will give the
+session a name. All blocks with the same session name share the same
+session. Using different session name enables concurrent sessions (even for
+the same interpreted language). E.g., @code{:session mysession}.
+@end itemize
@node noweb
@subsubsection @code{:noweb}
