diff --git a/docs/command-line.md b/docs/command-line.md
index 51eeb2f6..2b506f16 100644
--- a/docs/command-line.md
+++ b/docs/command-line.md
@@ -243,15 +243,23 @@ This option lists all available tests in a non-indented form, one on each line.
 
 Test cases are ordered one of three ways:
 
-
 ### decl
-Declaration order (this is the default order if no --order argument is provided). The order the tests were originally declared in. Note that ordering between files is not guaranteed and is implementation dependent.
+Declaration order (this is the default order if no --order argument is provided).
+Tests in the same TU are sorted using their declaration orders, different
+TUs are in an implementation (linking) dependent order.
+
 
 ### lex
-Lexicographically sorted. Tests are sorted, alpha-numerically, by name.
+Lexicographic order. Tests are sorted by their name, their tags are ignored.
+
 
 ### rand
-Randomly sorted. Test names are sorted using ```std::random_shuffle()```. By default the random number generator is seeded with 0 - and so the order is repeatable. To control the random seed see <a href="#rng-seed">rng-seed</a>.
+
+Randomly sorted. The order is dependent on Catch2's random seed (see
+[`--rng-seed`](#rng-seed)), and is subset invariant. What this means
+is that as long as the random seed is fixed, running only some tests
+(e.g. via tag) does not change their relative order.
+
 
 <a id="rng-seed"></a>
 ## Specify a seed for the Random Number Generator