Update tab.md - added a few comments about various tab stops for clarity.

Author: rasamassen

docs/usage/styles/tab.md

@@ -21,21 +21,21 @@ See [`Sample_02_TabStops`](/samples/Sample_02_TabStops.php) for more code sample
 
 ## Constants
 - Tab Stop
-  * `TAB_STOP_CLEAR`
-  * `TAB_STOP_LEFT`
-  * `TAB_STOP_CENTER`
-  * `TAB_STOP_RIGHT`
-  * `TAB_STOP_DECIMAL`
-  * `TAB_STOP_BAR`
-  * `TAB_STOP_NUM`
+  * `TAB_STOP_CLEAR`. Removes an existing tab.
+  * `TAB_STOP_LEFT`.
+  * `TAB_STOP_CENTER`.
+  * `TAB_STOP_RIGHT`.
+  * `TAB_STOP_DECIMAL`. All text is aligned around the first decimal character found within the text.
+  * `TAB_STOP_BAR`. Does not result in a tab stop but instead a vertical bar is drawn at the location.
+  * `TAB_STOP_NUM`. This is for backward compatibility and should be avoided in favor of paragraph indentation.
 
 - Tab Leader
-  * `TAB_LEADER_NONE`
-  * `TAB_LEADER_DOT`
-  * `TAB_LEADER_HYPHEN`
-  * `TAB_LEADER_UNDERSCORE`
-  * `TAB_LEADER_HEAVY`
-  * `TAB_LEADER_MIDDLEDOT`
+  * `TAB_LEADER_NONE`.
+  * `TAB_LEADER_DOT`.
+  * `TAB_LEADER_HYPHEN`.
+  * `TAB_LEADER_UNDERSCORE`.
+  * `TAB_LEADER_HEAVY`.
+  * `TAB_LEADER_MIDDLEDOT`.
 
 ## Options
 - `type`. Stop type. `TAB_STOP_CLEAR` is default.