Added comments explaining what a Match is

regex/matching.go

@@ -5,7 +5,12 @@ import (
 	"sort"
 )
 
-// a Match stores a slice of all the capturing groups in a match.
+// A Match represents a match found by the regex in a given string.
+// It is represented as a list of [Group]s, where the nth element contains
+// the indices matched by the nth capturing group. The element at index 0 is known
+// as the 0-group, and represents the contents of the entire match.
+//
+// See [Regex.FindSubmatch] for an example.
 type Match []Group
 
 // a Group represents a group. It contains the start index and end index of the match