update lang docs

edn/README.md

@@ -31,17 +31,12 @@ this is a `tek_input` keymap defined using ket:
 
 ## tokens
 
-ket has 5 "types":
+ket has 4 "types", represented by variants of the `Value` enum:
 
-* nil
+* `Num` - numeric literal
-* numeric literal
+* `Sym` - textual symbol
-* symbol
+* `Key` - textual key
-* key
+* `Exp` - parenthesized group of tokens
-* group
-
-### nil
-
-this does nothing.
 
 ### numeric literal
 
@@ -83,10 +78,10 @@ they are parsed in `tek_tui` and look like this:
 @ctrl-alt-shift-space
 ```
 
-### groups
+### parenthesized groups
 
-groups represent things like expressions or configuration statements,
+parenthesized groups represent things like expressions
-and look like this:
+or configuration statements, and look like this:
 
 ```edn
 (some-key :symbol (some/other-key @another-symbol 123) 456)