tweak

Author: tony

manuscript/02-terminal-fundamentals.md

@@ -90,9 +90,9 @@ The terminal interface can be best introduced by citing official specification
 laying out its technical properties, interfaces and responsibilities. This can
 be viewed in its [POSIX specification](http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap11.html).
 
-That's your TTY's, what you see when you move between them, on Linux / BSD
-systems, this you can switch between sessions via `<ctrl-alt-F1>` through
-`<ctrl-alt-F12>`.
+That's your TTY's, including text terminals and X sessions that live within
+them. On Linux / BSD systems, you can switch between sessions via
+`<ctrl-alt-F1>` through `<ctrl-alt-F12>`.
 
 ## Terminal emulators