From 68cda732a932a2ab40e4841ad6946d9d61400b0d Mon Sep 17 00:00:00 2001
From: Justin Poehnelt <jpoehnelt@google.com>
Date: Tue, 9 Nov 2021 18:56:42 +0000
Subject: [PATCH] docs(README): explain type guards

---
 README.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 80c957a6..22cd5b0b 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,8 @@
 
 This package provides [TypeScript guards](https://www.typescriptlang.org/docs/handbook/2/narrowing.html#using-type-predicates) for the Google Maps JavaScript API. 
 
+A type guard (or type predicate) is an expression that performs a runtime check that guarantees the type in some scope. Type guards are used to narrow the type of a variable or parameter.
+
 ## Documentation
 
 For the complete API check the [reference documentation](https://googlemaps.github.io/js-typescript-guards/index.html).
@@ -40,4 +42,4 @@ if (isLatLngLiteral(latLng)) {
   lat = latLng.lat();
   lng = latLng.lng();
 }
-```
\ No newline at end of file
+```