diff --git a/3.0/docs/jwt/index.md b/3.0/docs/jwt/index.md
index e2da854d..1d489c7f 100644
--- a/3.0/docs/jwt/index.md
+++ b/3.0/docs/jwt/index.md
@@ -1,7 +1,15 @@
-# Using JSON Web Token
+# JSON Web Token
 
 JSON Web Token is a library containing all JSON Web Token related APIs.
 
+### What is JWT?
+
+JWT is a standard for managing client tokens. Tokens are a form of identification and proof to the server. JWT is cryptographically signed, so it is not possible to falsify the validity of a JWT unless any of the following conditions is met:
+
+- A broken algorithm was used (such as MD5)
+- A weak signing key was used and brute-forced
+- The signing key used was leaked out to a third party
+
 ### Index
 
 - [JSON Web Signature](jws.md)
@@ -34,4 +42,4 @@ let package = Package(
 )
 ```
 
-Use `import JSON Web Token` to access JSON Web Token's APIs.
+Use `import JWT` to access JSON Web Token's APIs.