Add summary syntax table to readme

README.md

@@ -5,6 +5,27 @@ RFC 9535 JSONPath in Go
 
 The jsonpath package provides [RFC 9535 JSONPath] functionality in Go.
 
+## JSONPath Expressions
+
+A brief overview of RFC [9535 JSONPath] syntax:
+
+| Syntax Element     | Description**                                                         |
+| ------------------ | ----------------------------------------------------------------------- |
+| `$`                | root node identifier                                                    |
+| `@`                | current node identifier (valid only within filter selectors)            |
+| `[<selectors>]`    | child segment: selects zero or more children of a node                  |
+| `.name`            | shorthand for ['name']                                                  |
+| `.*`               | shorthand for [*]                                                       |
+| `..[<selectors>]`  | descendant segment: selects zero or more descendants of a node          |
+| `..name`           | shorthand for ..['name']                                                |
+| `..*`              | shorthand for ..[*]                                                     |
+| `'name'`           | name selector: selects a named child of an object                       |
+| `*`                | wildcard selector: selects all children of a node                       |
+| `3`                | index selector: selects an indexed child of an array (from 0)           |
+| `0:100:5`          | array slice selector: start:end:step for arrays                         |
+| `?<logical-expr>`  | filter selector: selects particular children using a logical expression |                                     |
+| `length(@.foo)`    | function extension: invokes  a function in a filter expression          |
+
 ## Package Stability
 
 The root `jsonpath` package is stable and ready for use. These are the main