[ExpressionLanguage] Add more information about the min/max functions

Author: Javier Eguiluz

reference/formats/expression_language.rst

@@ -172,7 +172,10 @@ This will print out ``true``.
 ``min()`` function
 ~~~~~~~~~~~~~~~~~~
 
-This function will return the lowest value::
+This function will return the lowest value of the given parameters. You can pass
+different types of parameters (e.g. dates, strings, numeric values) and even mix
+them (e.g. pass numeric values and strings). Internally it uses the :phpfunction:`min`
+PHP function to find the lowest value::
 
     var_dump($expressionLanguage->evaluate(
         'min(1, 2, 3)'
@@ -183,7 +186,10 @@ This will print out ``1``.
 ``max()`` function
 ~~~~~~~~~~~~~~~~~~
 
-This function will return the highest value::
+This function will return the highest value of the given parameters. You can pass
+different types of parameters (e.g. dates, strings, numeric values) and even mix
+them (e.g. pass numeric values and strings). Internally it uses the :phpfunction:`max`
+PHP function to find the highest value::
 
     var_dump($expressionLanguage->evaluate(
         'max(1, 2, 3)'