diff --git a/HOWTO b/HOWTO
index 03a0060..f8b488f 100644
--- a/HOWTO
+++ b/HOWTO
@@ -1064,8 +1064,11 @@
 		the job to exit. The same format as rate is used for read vs
 		write separation.
 
-rate_poisson=bool	When rate limited, try to simulate request flow under
-		Poisson process (instead of even distribution). Default: false.
+rate_poisson=bool	Real world random request flow follows Poisson process
+		(https://en.wikipedia.org/wiki/Poisson_process). With
+		rate_poisson=1, fio tries to simulate request flow under Poisson
+		process (instead of even distribution, which is the default).
+		Default: false.
 
 latency_target=int	If set, fio will attempt to find the max performance
 		point that the given workload will run at while maintaining a
diff --git a/fio.1 b/fio.1
index 99d9f9e..b8e31db 100644
--- a/fio.1
+++ b/fio.1
@@ -964,8 +964,10 @@
 is used for read vs write separation.
 .TP
 .BI rate_poisson \fR=\fPbool
-When rate limited, try to simulate request flow under Poisson process (instead
-of even distribution). Default: false.
+Real world random request flow follows Poisson process
+(https://en.wikipedia.org/wiki/Poisson_process). With \fBrate_poisson\fR=1, fio
+tries to simulate request flow under Poisson process (instead of even
+distribution, which is the default). Default: false.
 .TP
 .BI ratecycle \fR=\fPint
 Average bandwidth for \fBrate\fR and \fBratemin\fR over this number of